ists pe hater Sa es 3 toe ce 





Library of Che Theological Seminary 


PRINCETON - NEW JERSEY 
997 KE 


PRESENTED BY 


Drews ari svAet Ope 
Manson Professor of Bible 
Lafayette College 


ON (967) 4 L4 on LO ee ar ues 
LeConte, Joseph, 1823-1901. 
Evolution 











sions 





PV O EU LON = 


ITS NATURE, ITS EVIDENCES, AND ITS 
RELATION TO RELIGIOUS THOUGHT 


BY 
JOSEPH LE CONTE 


AUTHOR OF “RELIGION AND SCIENCE,” ETC. 
AND PROFESSOR OF GEOLOGY AND NATURAL HISTORY IN THE 
UNIVERSITY OF CALIFORNIA 





LIBRARY OF PRINCETON 
REVISED 


MAR 6 2000 







SECOND ED 


THEOLOGICAL SEMINARY 


NEW YORK 
D. APPLETON AND COMPANY 
1892 


CopyricutT, 1888, 1891, 
By D. APPLETON AND COMPANY. 


PREFACE TO THE SECOND EDITION. 


Tue three years which have elapsed since the pub- 
lication of the first edition of this work have been 
years of great activity of thought on many of the sub- 
jects treated therein. Some changes and additions 
seemed therefore imperatively called for. 

For example: There has sprung up recently among 
the foremost writers on evolution a warm discussion on 
the factors of evolution, their number and relative im- 
portance. I have therefore added a chapter (Chap. III, 
Part IT) on this subject—not, indeed, to discuss it fully 
(for this would be impossible in the limits of a chapter), 
but to put the mind of the reader in position to under- 
stand it and to judge for himself. 

Again: Every reader of the first edition must have 
remarked that there are many fundamental religious 
questions which I have not touched at all in Part III. 
I had avoided these because my own mind was not yet 
fully clear. I regarded what I then wrote as only a 
little leaven in a very large lump. I was willing to 
wait and let it work. In the mean time it has worked 
in my own mind, and I hope in the minds of others. 
I have therefore added two chapters to this part. In 
one I simply carry out to their logical consequences 


iv PREFACE TO THE SECOND EDITION. 


the doctrine of the Divine Immanency. This brings 
up the questions of /irst and Second Causes; of 
General and Special Providence ; of the WVatural and 
the Supernatural ; of Mind vs. Mechanics in Nature, 
etc., and shows the necessary changes of view which 
are enforced by the theory of evolution. 

In the other I take up very briefly “ Zhe Pelation 
of Evolution to the Doctrine of the Christ.” In the 
discussion of this I restrain myself strictly within the 
limits of the subject as stated above. 

The only other important changes are in Chapter LV, 
Part ITI, “ On the Relation of Man to Nature.” As I 
regard this as the most important chapter in the whole 
book, I have endeavored still further to enforee my 
view of the origin of man’s spirit, and especially to 
make it clearer by means of several additional illustra- 


tions. 
JosEPH LE Contr. 


BERKELEY, CAu., July 1, 1891. 


PREFACE TO THE FIRST EDITION. 


Tue subject of the following work may be expressed 
in three questions: What is evolution? Is it true? 
What then? Surely, there are no questions of the day 
more burning than these. Much has been written on 
each of them, addressed to different classes of minds: . 
some to the scientific, some to the popular, and some to 
the religious and theological; but nothing has yet ap- 
peared which covers the whole ground and connects 
the different parts together. Much, very much has been 
written, especially on the nature and the evidences of 
evolution, but the literature is so voluminous, much of 
it so fragmentary, and most of it so technical, that even 
very intelligent persons have still very vague ideas on 
the subject. I have attempted to give (1) a very con- 
cise account of what we mean by evolution, (2) an out- 
line of the evidences of its truth drawn from many differ- 
ent sources, and (3) its relation to fundamental religious 
beliefs. I have determined, above all, to make a book 
so small that it may be read through without much ex- 
pense of time and patience. But the subject is so large 
that in order to do so it was necessary to sacrifice all 
but what was most essential, and to forego all redun- 


vi PREFACE TO THE FIRST EDITION. 


dancy (the bane of so-called popular science) even at the 
risk of baldness and obscurity. Nevertheless, I hope 
that the first and second parts will be found not only 
interesting to the intelligent general reader, but even 
profitable to the special biologist. I have tried to 
make these parts as untechnical as possible, but I 
hope not on that account the less scientific. For I am 
among those who think that it is not necessary to be 
superficial in order to be popular—that science may be 
adapted to the intelligent popular mind without ceasing 
to be science. 

The third part seems to me still more important just 
.now. There is a deep and widespread belief in the 
popular mind, and even to some extent in the scientific 
mind, that there is something exceptional in the doc- 
trine of evolution as regards its relation to religious 
thought and moral conduct. Other scientific theories 
have required only some modifications of religious con- 
ceptions, but this utterly destroys the possibility of all 
religious belief by demonstrating a pure materialism. 
Now this, I believe, is _a complete misconception, 
Thinking men are fast coming to see this; some, in- 
deed, have mistaken the change for a reaction against 
evolution. It is a reaction not against evolution, but 
only against its materialistic implication. Evolution is 
more and more firmly established every year. The tide 
of conviction is one which knows no ebb. Some clear 
statement, in brief space, of its true relation to religious 
‘thought seems, therefore, very important at this time. 


BERKELEY, Cau., May, 1887. 


CONTENTS. 


PAR De 1 
WHAT IS EVOLUTION? 


CHAPTER I. 
ITS SCOPE AND DEFINITION. 


A type of evolution—Development of an eg 

Universality of evolution—Pervades all pares ats concerns all de- 
partments of thought--One half of all science—lIllustrated (1) 
by human body, (2) by solar system, (3) by society, (4) by earth, 
(5) by organic kingdom —The term evolution usually, but not 
rightly, confined to this last ; 

Definition of evolution—I. Progressive Ase pe eer in the Rea 
body, or the Ontogeniec series—In the animal scale, or the Tazo- 
nomic series—In the geological, or Phylogenic series—The three 
series similar, though not identical : . 

IT. Change according to certain laws—Three laws of succession of 
organic forms . 

(a) Law of differ Seddon Backs ates are Supers aeepacie 
separated into specialized forms—ITllustrated by fishes, by birds 
—Whole process of differentiation illustrated by growth and 
branching of a tree . : 

(6) Law of progress of the Pie Matere of sarifarrading alae 
with upward progress—Ilow far true, and how far false—Illus- 
trated by branching tree—Examples of this mistake in the 
popular mind—In the scientific mind 

(c) Law of cyclical movement—Shown in geological hater aes of 
mollusks, fishes, reptiles, mammals, man—I]lustrated again by 


PAGE 


1, 


11 


138 


viii CONTENTS. 


PAGE 
a branching tree—Increasing complexity as well as height— 
Illustrated by diagram. . ° eurl6 

The above three laws are laws of svolstion— Differentiation -SkeRn 
in the development of an egg, the type of evolution . : sen 

Progress of the whole—Not progress of all parts—Shown in the de- 
velopment of an egg : ; . . : weZe 


Cyclical movement—Less fandamnental than other iwoneshorn in 
Ontogeny of body, of mind—Increasing complexity—Necessity 
of continued advance—Otherwise deterioration—All these laws 
shown in progress of society—Differentiation shown—Progress 
of the whole but not of all parts shown—Cyclical movement 
shown—In social evolution, however, there is another element, 
viz., conscious voluntary progress—This kind of evolution con- 
fridted with the other. : : : : ; . 22 
III. Change by means of resident for beeThte is the point of dis- 
pute—Sense in which we use term resident forees—Does not 
touch question of origin of natural forces “ wee xs 
The two views of the origin of organic forms briefly se nicntad oe 
to whether natural or supernatural—As to variability, definite 
or indefinite—As to change from one species to another by 
transmutation or substitution—As to universality of law of con- 
tinuity . : ; ; . . . . . . 7 29 


CHAPTER II. 
THE RELATION OF LOUIS AGASSIZ TO THE THEORY OF EVOLUTION. 


General misunderstanding on this subject—Necessary to give sketch 
of history of the idea—Greeks, Lucretius, Swedenborg, and 
Kant—First scientific presentation by Lamarck—General char- 
acter of Lamarck’s views —Failed, and rightly so—Next, Cham- 
bers’s ‘ Vestiges of Creation”—lIts general character—Failed, 
and rightly so—Some think this unfortunate—Why not so— 
An obstacle must be removed and a basis laid . : ee aaa 

Lhe obstacle removed—Old views in regard to forces—Correlation of 
forees established—But vital force considered exception—There- 
fore living forms also supposed exception to mode of origin of 
other forms—Then vital forces also correlated—Therefore, a 
priort probable that living forms also correlated with other 
forms as to mode of origin—Thus obstacle removed . : - 35 


CONTENTS. ix 


PAGE 

The basis laid —Agassiz laid inductive basis of evolution, although he 
refused to build—He established the laws of evolution and per- 
fected the method of comparison—Importance of method dis- 
cussed—The method of notation—The method of experiment— 
The difficulty of applying these to life phenomena—Method of 
comparison shown—(1) In Taxonomic series—(2) In Ontogenic 
series—(3) In Phylogenic series—Cuvier the great worker by 
comparison in the Taxonomic series—Agassiz in the Ontogenic 
and Phylogenic—Agassiz also established the three laws of evo- 
lution given in previous chapter—Thus he laid foundation— 
Why he did not build—Supposed identity of evolution and ma- 
terialism—The obstacle being removed and the basis laid, when 
evolution again brought forward it was universally accepted, 
because the world was prepared—Place of Agassiz and Darwin 
compared—Formal science vs. piysical science—lIllustrated by 
relation of Kepler to Newton—Relation of Agassiz to time cos- 
mos similar to that of Kepler to space cosmos—So Darwin to 
Newton—Some reflections on the above—Gravitation is the law 
of space cosmos—Evolution of time cosmos—Of the divine 
spheral music gravitation is the chordal harmony and evolution 
the melody . : : : 2 - : : ; LOT 


PART -H. 
EVIDENCES OF THE TRUTH OF EVOLUTION. 


CHAPTER I. 
GENERAL EVIDENCES OF EVOLUTION AS A UNIVERSAL LAW. 


Evolution is continuity, causal relation, gradual becoming—Increasing 
acceptance of this idea—First accepted for inorganic forms, 
mountains, continents and seas, rocks and soils, earth as a 
whole, heavenly bodies—Therefore acknowledged for all inor- 
ganics—Influence of geology in bringing about this change— 
Organic forms: acknowledged for individuals, true for classes, 
orders, families, genera—Races and varieties also formed gradu- 
ally—Artificial species formed gradually—Examples of gradual 
changes in wild species—Hyatt’s researches—Other examples 
—Summing up of general evidencc—Sufficient ground for induc- 


“ CONTENTS. 


PAGE 


tion—But evolution is not only inductively probable but certain, 
axiomatic—It is the law of causation applied to forms, and 
therefore a necessary truth . ; : : , : : 


CHAPTER II. 


SPECIAL PROOFS OF EVOLUTION. 
Introductory. 


Special proofs necessary—Evolution, though certain, is not yet ac- 
cepted by the popular mind—Different departments from which 
proofs are drawn. ; ; : , ° ; ; . 

Origin of new organic forms ; the old view briefly stated—Necessary 
to give a brief statement of theories—Old view—Permanency 
of specific types—Supernatural origin of species—Centers of 
creation—Explanation of facts of geographical distribution— 
Of geological distribution—Modification of extreme view— 
Variability, but within limits—lIllustrated ; . : 

The new view briefly stated—Indefinite variability of organic forms— 
Effect of environment on rigid forms—On plastic forms—Taxo- 
nomic groups represent degrees of kinship : 

Factors of evolution—(1) Physical environment—(2) Use and Aes 
of organs—(3) Natural selection—(4) Sexual selection—(5) Physi- 
ological selection—Its necessity shown—Its operation explained 
—Compared with natural selection—UCause of variation unknown 
—Explanation of this is the next great step in the theory of 
evolution . : : 


CHAPTER III. 


53 


67 


68 


72 


73 


THE GRADES OF THE FACTORS OF EVOLUTION AND THE ORDER OF THEIR 


APPEARANCE. 


Factors of evolution restated; their grades and the order of their intro- 
duction shown—Lamarckian factors, first in order because they 
precede sexual reproduction—(1) Environment—(2) Use and 
disuse—With sexual reproduction selective factors introduced 
—(3) Natural selection—(4) Physiological selection—(5) Sexual 
selection—With man was introduced (6) the rational factor— 
In this process two striking stages—viz., the introduction of 
sex and the introduction of reason—Effect of each to hasten the 
steps of evolution—The last by far the greater change . . 


81 


CONTENTS xl 


PAGE 

Contrast between organic and human evolution—(1) The meaning of 
term fittest in each—(2) Destiny of the weak and helpless in 
each—(8) The nature of evolutionary transformation in each 
—(4) The law of strait and narrow way applied in each—(5) 
Human evolution is a different kind and ona higher plane . 88 

Application to some questions of the day. 

I. Neo-Darwinists, their position explained—Reasons for dissenting 
—(a) Lamarckian factors preceded all others—(b) Though now 
subordinate, they still underlie and condition all other factors— 

(c) Shown by comparison of phylogeny with ontogeny. ice 

II. Human progress not identical with organic evolution— Mistake 

' of the materialists—But neither is it wholly different, as some 
suppose . : : . 96 

III. Neo-Darwinism is fatal to Hones of ecard ena ee See 
may use frecly Lamarckian factors, but can not use natural 
selection in the same way as Nature does. : ; . ONS 


CHAPTER IV. 


SPECIAL PROOFS FROM THE GENERAL LAWS OF ANIMAL STRUCTURE, OR 
COMPARISON IN THE TAXONOMIC SERIES, 


General Principles. 


Analogy and homology—Defined and illustrated by examples—Wings 
and limbs—Lungs, gradual formation of, traced in the Taxo- 
nomic series—Traced in the Ontogenic series—Examples of 
homology in plants: tuber, cactus-leaf, acacia-leaf—Definitions 
repeated and further explained—Common origin is the only ex- 
planation of homology . ; : . 99 
Primary divisions of the animal Lip donee Teile Be of sah divi- 
sions is ability to trace homology—We take examples only from 
vertebrata and articulata—Compare to styles of architecture— 
To machines—To branching stem . . . ©. . «10% 


CHAPTER V. 
PROOFS FROM HOMOLOGIES OF THE VERTEBRATE SKELETON. 


Common general plan—In several respects—Strongly sugzestive 
of common origin—Details of structure demonstrative of the 
same * . e . . . * . . e . 111 


ae ) CONTENTS. 


PAGE 
Special homology of vertebrate limbs ‘ . : : 3 . 118 
Fore-limbs—Comparison of fore-limbs of mammals, birds, reptiles, 
and fishes, part for part—Gradual changes in collar-bone and 
coracoid—In position of elbow—In bones of forearm—lIn posi- 
tion of wrist—In the tread—The term manus—Number of toes 
—Modifications for flight in various animals—For swimming in 
whales and fishes. 4 : . 113 
Hind-limbs—Comparison of hind- Riinbe of paver mainmalset POR 
tion of knee—Of heel—Plantigrade and digitigrade—Degrees 
of the latter—Number of toes—General law in regard to num- 
ber of similar parts—Order of toe-dropping in artiodactyles— 
In perissodactyles . : ; é : : age b+ | 
Genesis of the horse—Changes in Pose oieNOni Fee Gee Ae of other 
parts of skeleton—Only natural explanation is derivation—Na- 
ture compared with man in mode of working—Angels—Griffins 
—Centaurs—Muscular and nervous systems—Visceral organs . 126 


CHAPTER VI. 
HOMOLOGIES OF THE ARTICULATE SKELETON. 


Illustrations from this type—Plan of structure entirely different— 
General plan of structure explained and modifications shown— 
Shrimp—Modification of segments and of appendages for vari- 
ous purposes: swimming, walking, eating, sense—lIllustrated 
by other crustaceans—By myriapods—By marine worms— 
Crabs—Embryonic development of crabs—insects—Modifica- 
tion of segments and appendages—Mouth parts of insects . 1382 

Lllustration of the law of differentiation—Cells—Segments—Individ- 
uals—Homologies in other departments of animals, but these 
are less familiar—Between primary groups, homology untrace- 
able in adult forms—But these also probably connected by com- 
mon origin—Different views as to origin of vertebrates . . 144 


CHAPTER VII. 
PROOFS FROM EMBRYOLOGY, OR COMPARISON IN THE ONTOGENIC SERIES. 


Resemblance of the three series—Frog, in Ontogeny passes through 
main stages of Taxonomy and Phylogeny—Resemblance only 
general—Many steps dropped out in Ontogeny . ; : . 148 


CONTENTS. 


(1) Ontogeny of tailless amphibians—The frog: fish stage, perenni- 
branch stage, caducibranch stage, aneural stage—Same stages 
in Phylogeny 

(2) Aortie arehes—Those of lizard Jeaeihat—OGah at alliage 
of fish—Change from one to the other in Ontogeny of a frog 
—Same changes in Phylogeny of lizard—Embryonic condition 
of mammalian heart and vessels—Gradual change and final con- 
dition in birds—In mammals—Gradual decrease in number of 
aortic arches as we go up the vertebrate scale—Cogency of the 
argument from aortic arches 

(8) Vertebrate brain—Fish brain—Brain of beatin. Ga sae 
man compared—Human brain passes through similar stages— 
Changes in complexity of structure in Taxonomy—Same changes 
in Ontogeny of mammals—Same in pe Se of reptiles, birds, 
mammals . ° ‘ ‘ 

Cephalization—Explanation of, in ede in ind 

(4) Fish-tails—Homocercal and heterocercal—V ertebrated Age non- 
vertebrated—Order of change in Ontogeny—Same in Phylogeny 
—Similar changes in birds’ tails in Ontogeny and Phylogeny— 
In other tailless animals—Examples from articulates, insects, 
crustaceans, ete. : . 

Illustration of the differ aiiahon of the hols aad igdomE De 
velopment of eggs of all kinds of animals—This a type of 
changes in Phylogeny—Why Ontogeny repeats Phylogeny—Law 
of acceleration . : . 

Proofs from rudimentary and ies 0 eFpanss BG She foam hal 
Teeth—Limbs—Hair—Olfactive organs—Examples from man; 
muscles, cecal appendage—Significance of useless organs 


CHAPTER VIII. 
PROOFS FROM GEOGRAPHICAL DISTRIBUTION OF ORGANISMS. 


Geographical faunas and floras—Conditions which limit . 
T emperature-regions—Illustrated by plants—In latitude and in ele- 
vation—Same in animal species 
More perfect definition of regions—Range of different ingsusenie 
groups—Gradual shadings on borders of range—Shadings out 
of individuals in number and vigor, but not in specific character 
—As if centers of origin—Effect of east and west barriers— 


PAGE 


. 150 


151 


. 162 
hil 


aces 


. 176 


. 179 


. 183 


. 184 


— CONTENTS. 


Temperature regions repeated south of the equator, but not 
species—As if centers of origin ‘ ; ; A 
Continental faunas and floras—Temperature zones continuous, but 
not species—Reason: ocean barriers—As if centers of origin— 
Polar regions: one. Why—Temperate zone—Different species 
in different continents—Species of United States and of Europe 
almost wholly different—<As if origin local—Exceptions—(1) 
Introduced species—(2) Hardy or else wide-migrating species— 
(3) Alpine species—Tropical zone of two continents still more 
different—Same true of south temperate zone . 
Subdivisions of continental faunas and floras—tIllustrated by fans 
and flora of United States : : : 
Special Tile! a lstalia © Maddeastape Galnpatoe=Wiiece mussels. 
Marine species—Same principles applicable—Therefore organic 
forms grouped in regions, sub-regions, provinces, etc.—Primary 
regions according to Wallace—According to Allen . : 
Theory of the origin of geographical diversity—Specific centers of 
creation—Objections to. The clement of time left out—Pro- 
gressive change in unlimited time, or evolution the only rational 
explanation—This connects with geographical changes in geo- 
logical times, especially the cna epoch—Geographical diver- 
sity in other times . . 
Most probable view of the gener aL pr el eee an Mies of 
change was the Glacial epoch—This, therefore, is the key to 
geographical distribution—Condition of things during the Gla- 
ci 
cal geography and in species—In Europe—Application of prin- 
ciples 





(1) Australia—Characteristics of its fina hatin nae of senha 
tion very early—Position of marsupials and monotremes in the 
Taxonomic scale—Australia isolated before the Tertiary—Effect 
of competition on evolution . : ; 

(2) Africa—African region ieineneoreo rece: of its mammals, 
indigenes, and invaders—HEffect of the invasion 

(8) Madagascar—Characteristics of its fauna—Relation to ifsent 
indigenes—Separated before the invasion—Significance of its 
lemurs 

(4) Island life—Two ee a idianda== etael Aa sTineteied by 
examples—(a) Continental islands—General character of fauna 


PAGE 


. 186 


. 188 


19k 


192 


. 192 


. 1938 


. 196 


. 200 


. 204 


. 205 


CONTENTS. “2 


PAGE 
—Illustrated by Madagascar, New Zealand, British Islands, 
coast-islands of California—Characteristics of the faunas of 
these explained—(b) Oceanie Jslands—Defined—Characteristics 

of faunas and their origin ; yee : e207 
(5) Alpine species—Characteristics of aha their origin NS a 
Migrations of Arctic species ant Glacial times, and their iso- 


lation on mountains . : : . 215 
Objection—Mode of change of species on fborde of Piceame eet 

ples—Sweet-gum—Sequoia : : 217 
Answer—Distribution of these forms in Gres ‘ond Gee migrations 

—They are remnants—Intermediate forms are extinct . . 219 


CHAPTER IX. 
PROOFS FROM VARIATION OF ORGANIC FORMS, ARTIFICIAL AND NATURAL, 


Limitation of the use of experiment in morphology—Unconscious ex- 
periments in breeding, and their results—Principles involved— 
Inheritance, immediate and ancestral—Effect of true breeding 
long continued—Method of selection illustrated by diagram— 
Formation of a race—Process the same in nature—Show select- 
ive effect of physical environment—Of organic environment— 

f migrations—Of unlimited time—Other factors of change, 
and their effects shown in nature and in domestication—Differ- 
ences between artificial and natural species. . 222 

First difference, reversion—The tendency to reversion deseritied = 
The reason explained—Illustrated by the case of the pointer . 229 

Seeond difference, intermediate SE vereasat ma these are elimi- 
nated in nature 5 . : é : . 232 

Third difference, eae ean Nataral Species are usually cross- 
sterile—Degrees of cross-sterility—Two bases of species, mor- 
pholog sexual 
repugnance and cross-sterility—Latter most essential—lIllus- 
trated by plants and hermaphrodite animals—Former only 
higher animals—Natural laws interfered with by domestication 
—lIllustrated by plants and animals . : : : : . 232 

Law of cross-breeding—Effect of close breeding—Of crossing varieties 
to a limit—The law investigated—Reproduction in lowest organ- 
isms—Fission—Gemmation—Internal gemmation—Sex intro- 
duced—Effect of, is funding of differences in offspring and 





a CONTENTS. 


PAGE 
tendency to variation—Sexual and non-sexual reproduction com- 
pared—Separation of sex elements—Of sex-individuals—Intro- 
duction of sex-attraction—Funding of greater differences in 
offspring—Crossing of varieties—Diagram illustrating effect in 
vigor—Effect also in plasticity—A pplication of these principles 
—Necessity of sexual isolation to produce species—Origin of 
cross-sterility and thus of species by Dr. Romanes’s idea—Why 
artificial varieties are cross-fertile—Geographical species some- 
times cross-fertile—Application of principles—Absence of inter- 
mediate links in natural species explained—Under what condi- 
tions such are found—Further explanation of this point— 
Illustrated by a growing tree . : . 236 

Objection answered—Intermediate links Saat to fs found asthe 
Answer (1) Imperfection of record. (2) The term species in- 
definite. (8) Transitions between all other taxonomic groups 
abundant. (4) Between species, also, both living and fossil— 
Of fossil, Planorbis of Steinheim—Other examples—(5) Why 
transition-forms are rare—Answer—Changes in every depart- 
ment of nature are paroxysmal—lIllustrated—So the steps of 
evolution paroxysmal—Critical periods in evolution—Causes of 
rapid advance—Apparent discontinuity between species—(1) 
changes paroxysmal—(2) Brooks’s idea—Male sex is the pro- 
gressive element—Illustrated by society—Effect of prosperous 
times—Mrs. Treat’s experiments—Hard times produce excess 
of males, and therefore tend to diversity—Summary . : . 248 

Objection—Kgyptian drawings and mummy plants, show no change 
—Answer (1) Time too short. (2) We are now in time of slow 
change. (8) All species don’t change, most become extinct. (4) 
Evolution is probably slower now than formerly—Reasons for 
so thinking—Organic evolution approaching completion—Other 


supposed objections. ‘ ; : ‘ a ; : . 265 
Origin of beauty—Explanation of, in higher animals—In flowering 
plants—But in many cases we can’t explain . : : . 269 


Incipient organs—Difficulty of explaining—But these are not objec- 
tions to the fact of evolution, but only to the sufficiency of the 
present theortes of evolution. Therefore, all discussion concerns 
Special theories. The fact of evolution is certain . : . 270 


CONTENTS. Xvli 


Pater aLre 


THE RELATION OF EVOLUTION TO RELIGIOUS 
THOUGHT. 


CHAPTER I> 


INTRODUCTORY. 
PAGE 


Evolution if true affects every department of thought—What will be 
its effect on religious beliefs ?—Objection that truth-seeker has 
nothing to do with effects—Answered . , : ; » 275 
Relation of the true and the good. : «217 
Relation of philosophy to life—The three necessary aleidonte of a 
rational philosophy—Application to the case in hand—<And the 
subject of Part III justified—Exaggerated fears—Diffcrent forms 
of the conflict of science and religion—(1) Heliocentric theory 
—First effect and final result—(2) Law of gravitation—Effect 
and result—(8) Antiquity of the earth and cosmos—Effect and 
result—(4) Antiquity of man—(5) Evolution . . . . 277 


CHAPTER II. 
THE RELATION OF EVOLUTION TO MATERIALISM. 


Supposed identity—Tendency of the age—Evolution does not differ 
in this regard from other laws of Nature—Absurdity of identifica- 
tion illustrated in many ways—(1) Effect of discovery of process 
of making—(2) Effect of new form of old truth—(3) Manner in 
which vexed questions are settled and rational philosophy 
found—lIllustrated—A true philosophy is a reconciliation of 
partial views—Three possible views of origin of individuals 
and of species ; two one-sided and partial, and the third com- 
bining, reconciling, and therefore rational—The only bar to 
speedy reconciliation is dogmatism—Theological and scientific 
—The appropriate rebuke for each—Thereforee volution does not 
differ from other laws in regard to its relation to materialism— 
Nevertheless, great changes in our traditional beliefs impending 
—Main changes are notions concerning God, Nature, and man, 
in their relations to one another : : : : 5 . 284 

2 


xviii CONTENTS. 


CHAPTER ITI. 
THE RELATION OF GCD TO NATURE. 
PAGE 
The issue in regard to this relation stated—The growth of the issue 
described—The old view of direct relation—The effect of science 
and the resulting view—The compromise—Destroyed by evolu- 
tion—The issue forced—The alternative view—Immanence of 
Deity—This view explained—Objection of idealism—Answered 
—It is not subjective idealism—Objection of pantheism—An- 
swer deferred —Objection that the view is incompatible with 
practical life-—-Answered. . » | - 1 oe ee 


CHAPTER IY. 
THE RELATION OF MAN TO NATURE. 


The two extreme views in this regard—They are views from different 
points, psychical and material—The latter very productive in 
modern times—But many fear the final effect—Reconciliation is 
possible—Scientific materialism has two branches—Physiologi- 
cal branch explained—Conclusion—Answer—Relation of psychic 
to brain changes is inscrutable—The mystery illustrated—Out- 
side and inside view—Different from other phenomena in this 
regard . : ‘ . : : : ; Z ‘ . 804 

Hvolution branch—Close relation of man to animals—Therefore must 
extend immortal spirit to animals—to plants—to all existence, 
and thus identify immortality with conservation of foree—Em- 
bryonic serics—Where did spirit enter ?—Evolution series— 
Where did spirit enter ?—Answer—Derived from Nature—The — 
true view of origin stated—Show that it is not in discord with 
other phenomena of evolution—The five planes of matter and of 
force—The change from one to another not gradual now nor in 
the evolution of natural forees—Consecutive births into higher 
forms—Every step of these changes taking place now—Rela- 
tion of these facts to immortality—The process briefly stated— 
Omnipresent divine energy individuated to separate entity in 
man—Anima of animals is spirit in embryo—Came to birth in 
man—TIllustrated in other ways—(1) By more or less completed 
water-drop—(2) By submergence and emergence—(3) By planet 
birth—(4) By physical birth—(5) By grades of organic indi- 


CONTENTS. 


viduality—(6) By the body as an instrument of communication 
between two worlds—Self-consciousness the sign of spirit-indi- 
viduality—Any animal conscious of self would be immortal— 
Similar changes in passing from animals to man in all other de- 
partments of psychic activity—Objection that other changes of 
energy not permanent; answered—Our view of origin compared 
with alternative views—Plato’s view—Orthodox view 
Some general conclusions—(1) Two scries of changes, brain-changes 
and mind-changes—The initiative in animals—In man—(2) 
Justification of term “‘ vital principle”—Becomes entity in man 
—(3) This view is a complete reconciliation of realism and 
nominalism—(4) No meaning in Nature without spirit—And no 
meaning in geological history without derivative origin of spirit 
—Material evolution finds its goal in man, psychic evolution in 
the divine man : ; : : , . 


CHAPTER V, 
THE RELATION OF GOD TO MAN, 


Question of revelation—Difficulty of the subject—Operation of divine 
spirit on spirit of man more direct than on Nature—This is reve- 
lation—This is no violation of law, but operation by higher law 
—Term supernatural is relative—Illustrated—There is but one 
kind of revelation, and this to all men in different degrees— 
Always imperfect, and therefore must be tried by reason . : 


CHAPTER VI. 


XIX 


PAGE 


Sole 


. 327 


831 


THE OBJECTION, THAT THE ABOVE VIEW IMPLIES PANTHEISM, ANSWERED, 


The objection stated and the general answer—In deepest questions 
single lines of thought lead to extreme views—Must follow other 


lines—These lead to personality : ; : . 535 
(1) Exact character of relation of God and of necessary ia to man’s 
freedom is inscrutable. : ‘ : . 838 


(2) On the inside of brain-changes we find personality—So on the i in- 
side of natural phenomena must also be person—In cither case 
science studies the outside only—In Nature all is mechanics on 
the outside, but all is mind on the inside—Thought behind brain- 
changes compels belief in same behind natural phenomena— 
Law of infinite expansion—lIllustrated by ideas of Space and 


XxX CONTENTS. 


Time—So also with idea of self—Infinite person inconceivable, 
but contrary is more inconceivable—lIllustrated by ideas of 
Space and Time ; . 
(8) Idea of Causation and of For Seneca Nor saithineeseona of 
the evolution of this idea—Final result is one infinite personal 
will—Expansion of idea of causal nexus between phenomena to 
the idea of one infinite cause . : ‘ 
(4) Idea of design also originates seth a nen dinate! but shane 
form—Expands to infinity—Same change produced by science 
in all our notions concerning God—Same in our sense of mys- 
tery—Same in our notions concerning ereation—Same in our 
conceptions of design—Thus, self-consciousness behind brain- 
changes compels belicf in God behind Nature—The closeness 
of connection in the one case necessitates closeness of connec- 
tion in the other—Every material change in Nature caused by 
a mental change behind Nature - : : : ; ; 


CHAPTER VII. 


PAGE 


. 338 


. 842 


845 


SOME LOGICAL CONSEQUENCES OF THE DOCTRINE OF THE DIVINE IMMANENCY. 


Religious thought subject to the Jaw of evolution; three main stages 351 
I. Conception of God—The three stages shown—(1) Anthropo- 
morphism—(2) Absentee landlordism—(3) Immanence . . 351 
II. Question of First and Second Causes—The three stages shown 
here—(1) All is First Cause but man-like—(2) Distinction of 
first and second causes introduced—(3) Identification of these 354 
Il. General and Special Providenee—The same three stages shown 
and the same outcome—viz., identification : . . 855 
IV. Natural and the super obra athe same stages a the same 
final identification—Question of miracles . : . 855 
V. Question of design or mind in Nature—The same three stapes 
and the same solution shown here—Confusion in the minds of 
modern writers ; Pied w ese 
VI. Question of mode of er eitom Old ad new views sone . 858 


CHAPTER VIII. 
RELATION OF EVOLUTION TO THE IDEA OF THE CHRIST. 


Comparison of organic with human evolution—The idea of the first 
is man, of the second is the Christ—Definition of the Christ as 


CONTENTS. 


ideal man—The Christ ought to differ from us in a superhuman 
way—Shown by several illustrations—The Christ, as ideal man, 
a true object of rational worship—The ideal of organic evolu- 
tion comes at the end—Ideal of human evolution must come in 
the course—Objection that there are many partial ideals an- 
swered—Relative vs. absolute moral ideal : : 


CHAPTER IX. 


THE RELATION OF EVOLUTION TO THE PROBLEM OF EVIL. 


The difficulty of the problem—The light on it by evolution—Evii 
must be based on the constitution of Nature and therefore uni- 
versal—Some of its forms : : : 

(1) Physical evil in animal iengdent-Condiane of organic evolu- 
tion is struggle with an apparently inimical environment—In 
its course it seems evil—Loolking back from the end it is 
good : ; 

(2) Physical evil in Pidiion Fs paneer sonaiion of eet 
evolution is also struggle with a seeming evil environment—But 
looking back from the end this evil is also seen to be good— 
Without it man would never have emerged from animality . 

(3) Organic evil—Disease—This also is the necessary condition of 
acquisition of knowledge of organic Nature—In the course of 
evolution it seems evil, but from the end it is seen to be good— 
In the physical world, laws of Nature are beneficent in their 
general operation, and only evil in their specific operation through 
our ignorance . : ; . 

(4) Moral evil—Moral fee ie ies Hevecn Hie and other 
forms of evil—Can this also be transmuted into good ?—This is 
only the highest form of evil, and therefore subject to the same 
laws of evolution—Here also elevation comes only through 
knowledge and power, and these only through struggle with ap- 
parent evil—In course it seems evil, looking back from end it 
is seen to be good to the race—In all, therefore, the individual 
is sacrificed to the race, but impossible here—A way of escape 
found in the nature of a moral being—In this case not only 
final victory for the race, but also within the power of the in- 
dividual—In this case success is in proportion to honest effort 
in right spirit—Roots of evil in the necessary law of evolution 


Xx1 


PAGE 


. 360 


. 865 


. 365 


366 


. 367 


xxii CONTENTS. 


PAGE 
-It is the necessary condition of all progress—Without it a 
moral being is impossible—From philosophic point of view 
things are not good and evil, but only higher and lower—All 
things good in their places—Kvil is discord—Good is due rela- 
tion—Action and reaction of higher and lower is the necessary 
ndition of true virtue . . ; . : : : . 369 


Pe Ave Dae 


WHAT IS EVOLUTION? 





CHAPTER I. 


ITS SCOPE AND DEFINITION. 


A Type of Evolution—LEvery one is familiar with} 
the main facts connected with the development of an) 


egg. We all know that it begins as a microscopic germ- 
cell, then grows into an egg, then organizes into a chick, 


and finally grows into a cock; and that the whole pro-_ 


cess follows some general, well-recognized law. Now, - 


this process is evolution. It is more—it is the type of 
all evolution. It is that from which we get our idea of — 
evolution, and without which there would be no such | 


word. Whenever and wherever we find a process of - 


change more or less resembling this, and following laws : 


similar to those determining the development of an egg, . 


we call it evolution. 


Universality of Evolution.—Kvolution as a process is | 


not confined to one thing, the egg, nor as a doctrine is 


it confined to one department of science—biology. The 


process pervades the whole universe, and the doctrine 


concerns alike every department of science—yea, every | 
department of human thought. It is literally one half - 


of all science. Therefore, its truth or falseness, its ac- 


4. WHAT IS EVOLUTION ? 


iceptance or rejection, is no trifling matter, affecting only 
‘one small corner of the thought-realm. On the con- 
trary, it affects profoundly the foundations of philos- 
ophy, and therefore the whole domain of thought. It 
determines the whole attitude of the mind toward Na- 
‘ture and God. 

I have said evolution constitutes one half of all sci- 
ence. This may seem to some a startling proposition. I 
stop to make it good. 

Every system of correlated parts may be studied from 
two points of view, which give rise to two departments 
of science, one of which—and the greater and more com- 
plex—is evolution. The one concerns changes within 
the system by action and reaction between the parts, 
producing equilibrium and stability ; the other concerns 
the progressive movement of the system, as a whole, to 
higher and higher conditions—the movement of the 
point of equilibrium itself, by constant slight disturb- 
ance and readjustment of parts on a higher plane, with 
more complex inter-relations. The one concerns the 
laws of sustentation of the system, the other the laws 
of evolution. ‘The one concerns things as they are, the 
other the process by which they become so. Now, Nature 
as a whole is such a system of correlated parts. Every 
department and sub-department of Nature, whether it be 
the solar system or the earth, or the organic kingdom, or 
human society, or the human body, is such a system of 
correlated parts, and is therefore subject to evolution. 
We can best make this thought clear by examples: 


ITS SCOPE AND DEFINITION. 5 


1. Take, then, the human body. This complex and 
beautiful system of correlated and nicely-adjusted parts 
may be studied in a state of maturity and equilibrium, 
in which all the organs and functions by action and 
reaction co-operate to produce perfect stability, health, 
and physical happiness. This study is physiology. Or 
else the same may be studied in a state of progressive 
change. Now, we perceive that the stability is never 
perfect—the point of equilibrium is ever moving. By 
the ever-changing number and relative power of the co- 
operating parts the equilibrium is ever being disturbed, 
only to be readjusted on a higher plane, with still more 
beautiful and complex inter-relations. This is growth, 
development, evolution. Its study is called embryology. 
2. Take another example—the solar system. We may 
study sun, planets, and satellites in their mutual actions 
and reactions, co-operating to produce perfect equilib- 
rium, stability, beautiful order, and musical harmony. 
This is the ideal of physical astronomy as embodied in 
Laplace’s ‘‘ Mécanique Céleste.” Or we may study the 
same in its origin and progressive change. Now, we per- 
ceive that equilibrium and stability are never absolutely 
perfect, but, on the contrary, there is continual disturb- 
ance with readjustment on a higher plane—continual in- 
troduction of infinitesimal discord, only to enhance the 
grandeur and complexity of the harmonic relations. 
This is the nebular hypothesis—the theory of the devel- 
opment of the solar system. It is cosmogony ; it is evo- 
lution. 3. Again: society may be studied in the mutual 


6 WHAT IS EVOLUTION? 


play of all its social functions so adjusted as to produce 
social equilibrium, happiness, prosperity, and good goy- 
ernment. This is social statics. But equilibrium and 
stability are never perfect. Permanent social equilibri- 
um would be social stagnation and decay. Therefore, we 
must study society also in its onward moyvement—the 
equilibrium ever disturbed, only to be readjusted on a 
higher plane with more and more complexly inter-related 
parts. This is dynamics—social progress. It is evolu- 
tion. 4. Again: the earth, as a whole, may be studied 
in its present forms, and the mutual action of all its parts 
—lands and seas, mountains and valleys, rivers, gulfs, 
and bays, currents of air and ocean—and the manner in 
which all these, by action and reaction, co-operate to pro- 
duce climates and physical conditions such as we now 
find them. ‘This is physical geography. Or, we may 
study the earth in its gradual progress toward its pres- 
ent condition—the changes which have taken place in 
all these parts, and consequent changes in climate ; in a 
word, the gradual process of becoming what it now is. 
This is physical geology—it is evolution. 5. Lastly, we 
may study the whole organic kingdom in its entirety 
as we now find it—the mutual relation of different 
classes, orders, genera, and species to each other and to 
external conditions, and the action and reaction of these 
in the struggle for life—the geographical distribution of 
species and their relation to climate and other physical 
conditions, the whole constituting a complexly adjusted 
and permanent equilibrium. ‘This is a science of great 


ITS SCOPE AND DEFINITION. i 


importance, but one not yet distinctly conceived, much 
less named.* Or, we may study the same in its gradual 
progressive approach, throughout all geological times, 
toward the present condition of things, by continual 
changes in the parts, and therefore disturbance of equi- 
librium and readjustment on a higher plane with more 
complex inter-relations. This is development of the 
organic kingdom. In the popular mind it is, par eacel- 
lence, evolution. 

We might multiply examples without limit. There 
are the same two points of view on all subjects. As 
already said, in the one we are concerned with things 
as they are; in the other, with the process by which 
they became so. This ‘‘ law of becoming” in all things 
—this universal law of progressive inter-connected change 
—may be called the law of continuity. We all recog- 
nize the universal relation of things, gravitative or 
other, in space. This asserts the universal causal rela- 
tion of things in ¢#ime. This is the universal law of 
evolution. 

But it has so happened that in the popular mind the 


ee 


term evolution is mostly confined to the development of | 


the organic kingdom, or the law of continuity as applied 


to this department of Nature. The reason of this is that — 


eee 


this department was the last to acknowledge the suprem- © 


acy of this law; this is the domain in which the advo- : 


cates of supernaturalism in the realm of Nature had 





* The term Chorology, used by Haeckel, nearly covers the ground. 


8 WHAT IS EVOLUTION? 


made their last stand. But it is wholly unphilosophical 
thus to limit the term. If there be any evolution, par 
excellence, it is evolution of the individual or embryonic 
development. This is the clearest, the most familiar, 
and most easily understood, and therefore the type of 
evolution. We first take our idea of evolution from this 
form, and then extend it to other forms of continuous 
change following a similar law. But, since the popular 


-mind limits the term to development of the organic 


kingdom, and since, moreover, this is now the battle- 
ground between the advocates of continuity and discon- 
tinuity—of naturalism and supernaturalism in the realm 
of Nature—what we shall say will have reference chiefly 
to this department, though we shall illustrate freely by 
reference to other forms of evolution. 


DEFINITION OF EVOLUTION. 


Kyolution is (1) continuous progressive change, (2) 


according to certain laws, (3) and by means of resident 
forces. It may doubtless be defined in other and per- 


haps better terms, but this suits our purposes best. 


Embryonic development is the type of evolution. It 


will be admitted that this definition is completely real- 
ized in this process. The change here is certainly con- 
tinuously progressive; it is according to certain well- 
ascertained laws; it is by forces (vital forces) resident 
in the egg itself. Is, then, the process of change in 
the organic kingdom throughout geologic times like 
this? Does it correspond to the definition given 


ITS SCOPE AND DEFINITION. 9 


above ? Does ir also deserve the name of evolution’? 
We shall see. 

I. Progressive Change.—Every individual animal body 
—say man’s—has become what it now is by a gradual 
process. Commencing as a microscopic spherule of liv- 
ing but apparently unorganized protoplasm, it gradually 
added cell to cell, tissue to tissue, organ to organ, and 
function to function; thus becoming more and more 
complex in the mutual action of its correlated parts, as 
it passed successively through the stages of germ, egg, 
embryo, and infant, to maturity. This ascending series 
of genetically connected stages is called the embryonic or 
Ontogenic series.* 

There is another series the terms of which are coex- 
istent, and which, therefore, is not in any sense a genetic 
or development series, but which it is important to men- 
tion, because to some degree similar to and illustrative of 
the last. Commencing with the lowest unicelled micro- 
scopic organisms, and passing up to the animal scale, as 
it now exists, we tind a series of forms similar, though 
not identical, with the last. Here, again, we find cell 
added to cell, tissue to tissue, organ to organ, and func- 
tion to function, the animal body becoming more and 
more complex in structure, in the mutual action of its 
correlated parts, and the mutual action with the environ- 
ment, until we reach the highest complexity of structure 
and of internal and external relations only in the highest 


~~ 


* Ontos-gennao (individual-making, or genesis of the individual). 


10 WHAT IS EVOLUTION? 


animals. This ascending series may be called the natural 
history series ; or, the classification or Taxonomic series.* 
The terms of this series are, of course, not genetically 
connected ; at least, not directly so connected. In what 
way they are connected, and how the series comes to be 
similar to the last, we shall see by-and-by. 

Finally, there is still a third series, the grandest and 
most fundamental of all, but only recently recognized, 
and therefore still imperfectly known. Commencing 
with the earliest organisms, the very dawn of life, in 
the very lowest rocks, and passing onward and upward 
through Eozoic, Paleozoic, Mesozoic, Cenozoic, to the 
Psychozoic or present time, we again find first the lowest 
forms, and then successively forms more and more com- 
plex in structure, in the interaction of correlated parts 
and in interaction with the environment, until we reach 
the most complex internal and external relations, and 
therefore the highest structure only in the present time.f 
This series we will call the geological or phylogenic se- 
‘ries.$ According to the evolution theory, the terms of 
this series also are genetically connected. It is, there- 
fore, an evolution series. Furthermore, it is the most 
fundamental of the three series, because it is the cause 
| of the other two. The Ontogenic series is like it because 
it is a brief recapitulation, through heredity, as it were 
from memory, of its main points. The Taxonomic series — 





* Taxis, nomos (relating to science of arrangement). 
+ This statement is general; it will be modified hereafter. 
t Piule-gennao (kind-making); genesis of the race. 


ITS SCOPE AND DEFINITION. 11 


is like it because the rate of advance along different lines 
was different in every degree, and therefore every stage 
of the advance is still represented in a general way 
among existing forms. Some of these points will be ex- 
plained more fully in future chapters, in connection with 
the evidences of the truth of evolution. 

It will be admitted, then, that we find progressive | 
change in organic forms throughout geological times. — 
This is the first point in the definition of evolution. 

II. Change according to Certain Laws.—We have 
shown continuously progressive change in organic forms 
during the whole geologic history of the earth, similar 
in a general way to that observed in embryonic develop- 
ment. We wish now to show that the laws of change 
are similar in the two cases. What, then, are the laws of 
succession of organic forms in geologic times? I have 
been accustomed to formulate them thus: a._The law of 
_ differentiation ; 6. The law of progress of the whole; ec. 
The law of cyclical movement.* We will take up these 
and explain them successively, and then, afterward, show 
that they are also the laws of embryonic development, 
and therefore the laws of evolution. 

a. Law of Differentiation—It is a- most significant 
fact, to which attention was first strongly directed by 
Louis Agassiz, that the earliest representatives of any 
group, whether class, order, or family, were not what we 


* This formulation of the laws of organic succession was given by me 
in 1860, before I knew anything of either Darwin’s or Spencer’s evolu- 
tion. They were my own mode of formulating Agassiz’s views. 


3 


12 WHAT IS EVOLUTION? 


would now call typical representatives of that group; 
but, on the contrary, they were, in a wonderful degree, 
connecting links; that is, that along with their distinc- 
tive classic, ordinal, or family characters they possessed 
also other characters which connected them closely with 
other classes, orders, or families, now widely distinct, 
without connecting links or intermediate forms. For 
example: The earliest vertebrates were fishes, but not 
typical fishes. On the contrary, they were fishes so 
closely connected by many characters with amphibian 
reptiles, that we hardly know whether to call some of 
them reptilian fishes, or fish-like reptiles. From these, 
as from a common vertebrate stem, were afterward sepa- 
rated, by slow changes from generation to generation, in 
two directions, the typical fishes and the true reptiles. 
So, also, to take another example, the first birds were far 
different from typical birds as we now know them. They 
were, on contrary, birds so reptilian in character, that 
there is still some doubt whether bird-characters or rep- 
tilian characters predominate in the mixture, and there- 
fore whether they ought to be called reptilian birds or 
bird-like reptiles. From this common stem, the more 
specialized modern reptiles branched off in one direction 
and typical birds in another, and intermediate forms be- 
came extinct; until now, the two classes stand widely 
apart, without apparent genetic connection. This sub- 
ject will be more fully treated hereafter, and other ex- 
amples given. ‘These two will be sufficient now to make 
the idea clear. 


ITS SCOPE AND DEFINITION. 13 


Such early forms combining the characters of two or 
more groups, now widely separated, were called by Agas- 
siz connecting types, combining types, synthetic types, 
and sometimes prophetic types; by Dana, comprehen- 
sive types; and by Huxley, generalized types. They are 
most usually known now as generalized types, and their 
widely-separated outcomes specialized types. ‘Thus, in 
general, we may say that the widely-separated groups of 
the present day, when traced back in geological times, 
approach one another more and more until they finally 
unite to form common stems, and these in their turn 
unite to form acommon trunk. From such a common 
trunk, by successive branching and rebranching, each 
branch taking a different direction, and all growing wider 
and wider apart (differentiation), have been gradually 
generated all the diversified forms which we see at the 
present day. The last leafy ramifications—flower-bear- 
ing and fruit-bearing—of this tree of life, are the fauna 
and flora of the present epoch. The law might be called 
a law of ramification, of specialization of the parts, and 
diversification of the whole. 

b. Law of Progress of the Whole.—Many imagine) 
that progress is the one law of evolution ; in fact, that 
evolution and progress are coextensive and convertible’ 
terms. They imagine that in evolution the movement 
must be upward and onward in all parts; that degener- | 
ation is the opposite of evolution. This is far from the | 
truth. There is, doubtless, in evolution, progress to | 
higher and higher planes; but not along every line, nor 


14 WHAT IS EVOLUTION? 


inevery part; for this would be contrary to the law of 
differentiation. It is only progress of the whole organic 
kingdom in its entirety. We can best make this clear 
by an illustration. A growing tree branches and again 
branches in all directions, some branches going upward 
some sidewise, and some downward—anywhere, every- 
where, for light and air; but the whole tree grows ever 
taller in its higher branches, larger in the circumference 
of its outstretching arms, and more diversified in struct- 
ure. Even so the tree of life, by the law of differentia- 
tion, branches and rebranches continually in all direc- 
tions—some branches going upward to higher planes 
(progress), some pushing horizontally, neither rising 
nor sinking, but only going farther from the general- 
ized origin (specialization) ; some going downward (de- 
generation), anywhere, everywhere, for an unoccupied 
place in the economy of Nature, but the whole tree 
grows ever higher in its highest parts, grander in its 
proportions, and more complexly diversified in its 
structure. | 

It may be well to pause here a moment to show how 
this mistaken identification of evolution with progress 
alone, without modification by the more fundamental 
laws of differentiation, has given rise to misconceptions 
in the popular and even in the scientific mind. The bi- 
ologist is continually met with the question, ‘‘Do you 
mean to say that any one of the invertebrates, such, for 
instance, as a spider, may eventually, in the course of 
successive generations, become a vertebrate, or that a dog 


ITS SCOPE AND DEFINITION. 15 


or a monkey is on the highway to become a man?” By 
no means. There is but one straight and narrow way to 
the highest in evolution as in all else, and few there be 
that have found it—in fact, probably two or three only 
at every step. The animals mentioned above have di- 
verged from that way. In their ancestral history, they 
have missed the golden opportunity, if they ever had 
it. It is easy to go on in the way they have chosen, 
but impossible to get back on the ascending trunk- 
_iine. To compare again with the growing tree, only 
one straight trunk-line leads upward to the terminal 
bud. <A branch once separated must grow its own way, 
if it grow at all. 

Of the same nature is the mistake of some extreme 
evolutionists, such as Dr. Bastian and Professor Haeckel, 
and of nearly all anti-evolutionists, viz., that of imagin- 
ing that the truth of evolution and that of spontaneous 


generation must stand or fall together. On the con- | 


trary, tf life did once arise spontaneously from any lower | 


forces, physical or chemical, by natural process, the con- | 


ditions necessary for so extraordinary a change could | 
hardly be expected to occur but once in the history of the | 
earth. They are, therefore, now, not only unreproduci- | 


ble, but unimaginable. Such golden opportunities do 
not recur. LHvyolution goes only onward. Therefore, the 


certian 


ue 


impossibility of the derivation of life from non-life now, | 


is no more an argument against such a derivation once, | 


aoe 


than is the hopelessness of a worm ever becoming a Ver- | 
tebrate now, an argument against the derivative origin | 


16 WHAT IS EVOLUTION ? 


of vertebrates. Doubtless if life were now extinguished 
from the face of the earth, it could not again be rekin- 
dled by any natural process known to us; but the same is 
probably true of every step of evolution. If any class— 
for example, mammals—were now destroyed, it could not 
be re-formed from any other class now living. It would 
be necessary to go back to the time and conditions of the 
separation of this class from the reptilian stem. There- 
fore, the falseness of the doctrine of abiogenesis,* so far 
from being any argument against evolution, is exactly 
what a true conception of evolution and knowledge of its 
laws would lead us to expect. 

c. Law of Cyclical Movement.—The movement of evyo- 
lution has ever been onward and upward, it is true, but 
not at uniform rate in the whole, and especially in the 
parts. On the contrary, it has plainly moved in succes- 
sive cycles. The tide of evolution rose ever higher and 
higher, without ebb, but it nevertheless came in succes- 
sive waves, each higher than the preceding and overborne 
by the succeeding. ‘These successive cycles are the dy- 
nasties or reigns of Agassiz, and ages of Dana ; the reign 
of mollusks, the reign of fishes, of reptiles, of mammals, 
and finally of man. During the early Paleozoic times 
(Cambrian and Silurian) there were no vertebrates. + 
But never in the history of the earth were mollusks of 
greater size, number, and variety of form than then. 


* Genesis without previous life—spontaneous generation. 
+ Fishes were first introduced in the later Silurian; but became 
dominant in the Devonian. 


ITS SCOPE AND DEFINITION. 1% 


They were truly the rulers of these early seas. In the 
absence of competition of still higher animals, they had 
things all their own way, and therefore grew into a great 
monopoly of power. In the later Paleozoic (Devonian) 
fishes were introduced. ‘They increased rapidly in size, 
number, and variety ; and being of higher organization 
they quickly usurped the empire of the seas, while the 
mollusca dwindled in size and importance, and sought 
safety in a less conspicuous position. In the Mesozoic 
times, reptiles, introduced a little earlier,* finding con- 
genial conditions and an unoccupied place above, rapidly 
increased in number, variety, and size, until sea and land 
seem to have swarmed with them. Never before or since 
have reptiles existed in such numbers, in such variety 
of form, or assumed such huge proportions; nor have 
they ever since been so highly organized as then. They 
quickly became rulers in every realm of Nature—rulers of 
the sea, swimming reptiles ; rulers of the land, walking 
reptiles ; and rulers of the air, flying reptiles. In the un- 
equal contest, fishes therefore sought safety in subordina- 
tion. Meanwhile mammals were introduced in the Meso- 
zoic, but small in size, low in type (marsupials), and by 
no means able to contest the empire with the great rep- 
tiles. But in the Cenozoic (Tertiary) the conditions ap- 
parently becoming favorable for their development, they 
rapidly increased in number, size, variety, and grade of 
organization, and quickly overpowered the great reptiles, 


* Amphibians were introduced in the Carboniferous, but true reptile 
not until the Permian, 


18 WHAT IS EVOLUTION? 


which almost immediately sank into the subordinate po- 
sition in which we now find them, and thus found com- 
parative safety. Finally, in the Quaternary, appeared 
man, contending doubtfully for a while, with the great 
mammals, but soon (in Psychozoic) acquiring mastery 
through superior intelligence. The huge and dangerous 
mammals were destroyed and are still being destroyed ; 
the useful animals and plants were preserved and made 
subservient to his wants; and all things on the face of 
the earth are being readjusted to the requirements of his 
rule. In all cases it will be observed that the rulers were 
such because, by reason of strength, organization, and in- 
telligence, they were fittest to rule. There is always room 
at the top. To illustrate again by a growing tree: This 
successive culmination of higher and higher classes may 
be compared to the flowering and fruiting of successively 
higher and higher branches. Each uppermost branch, 
under the genial heat and light of direct sunshine, re- 
ceived in abundance by reason of position, grew rapidly, 
flowered, and fruited ; but quickly dwindled when over- 
shadowed by still higher branches, which, in their turn, 
monopolized for a time the precious sunshine. 

But observe, furthermore : when each ruling class de- 
clined in importance, it did not perish, but continued in 
a subordinate position. Thus, the whole organic king- 
dom became not only higher and higher in its highest 
forms, but also more and more complex in its structure 
and in the interaction of its correlated parts. The whole 
process and its result is roughly represented in the ac- 


ITS SCOPE AND DEFINITION. 19 





Silurian. Devon. and Carb. Mesozoic. Tert’y and Quat. Present, 


Fig. 1. 


companying diagram, Fig. 1, in which A B represents 
the course of geological time and the curve, the rise, 
culmination, and decline of successive dominant classes. 


THE ABOVE THREE LAWS ARE LAWS OF EVOLUTION. 


These three laws we have shown are distinctly recog- 
nizable in the succession of organic forms in the geologi- 
cal history of the earth. They are, therefore, undoubt- 
edly the general laws of succession. Are they also laws 
of evolution ? Are they also discoverable in embryonic 
development, the type of evolution? ‘They are, as we 
now proceed to show: 

Differentiation.—In reproduction the new individual 
appears: 1. As a germ-cell—a single microscopic living 
cell. 2. Then, by growth and multiplication of cells, it 
becomes an egg. This may be characterized as an aggre- 
gate of similar cells, and therefore is not yet differen- 
tiated into tissues and organs. In other words, it is not 
yet visibly organized ; for organization may be defined as 
the possession of different parts, performing different 
functions, and all co-operating for one given end, viz., 
the life and well-being of the organism. 38. Then com- 
mences the really characteristic process of development, 


20 WHAT IS EVOLUTION ? 


viz., differentiation or diversification. The cells are at 
first all alike in form and function, for all are globular 
in form, and each performs all the functions necessary 
for life. From this common point now commences de- 
velopment in different directions, which may be com- 
pared to a branching and rebranching, with more and 
more complex results, according as the animal is higher 
in the scale of organization and advances toward a state 
of maturity. First, the cell-aggregate (egg) separates into 
three distinct layers of cells, called ecto-blast, endo-blast, 
and meso-blast. These by further differentiation form the 
three fundamental groups of organs and functions, viz., 
the nervous system, the nutritive system, and the blood 
system: the first presiding over the exchange of force or 
influence, by action and reaction with the environment, 
and between the different parts of the organism ; the sec- 
ond presiding over the exchange of matter with the envi- 
ronment, by absorption and elimination ; the third presid- 
ing over exchanges of matter between different parts of 
the organism. The first system of functions and organs 
may be compared to a system of telegraphy, foreign and 
domestic ; the second to foreign commerce; the third to 
an internal carrying-trade. Following out any one of 
these groups in higher animals, say the nervous system, it 
quickly differentiates again into two sub-systems, viz., cer- 
ebro-spinal and ganglionic, each having its own distinctive 
functions, which we can not stop to explain. ‘ Then the 
cerebro-spinal again differentiates into voluntary and re- 
flex system-. All of these have meanwhile separated into 


ITS SCOPE AND DEFINITION. 21 


sensory and motor centers and fibers. Then, taking only 
the sensory fibers, these again are differentiated into five 
special senses, each having a wholly different function. 
Then, finally, taking any one of these, say the sense of 
touch or feeling, this again is differentiated into many 
kinds of fibers, each responding to a different impression, 
some to heat, others to cold, still others to pressure, etc. 
We have taken the nervous system ; but the same differ- 
entiation and redifferentiation takes place in all other 
systems, and is carried to higher and higher points ac- 
cording to the position in the scale of the animal which 
is to be formed. 

Or, to vary the mode of presentation a little, the cells 
of the original aggregate, commencing all alike, imme- 
diately begin to take on different forms, in order to per- 
form different functions. Some cells take on a certain 
form and aggregate themselves to form a peculiar tissue 
which we call muscle, and which does nothing else, can 
do nothing else, than contract under stimulus. Another 
group of cells take on another peculiar form and aggre- 
gate themselves to form another and very different tis- 
gue, viz., nervous tissue, which does nothing and can do 
nothing but carry influence back and forth between the 
great external world and the little world of consciousness 
within. Still another group of cells take still another 
form and aggregate to form still another tissue, viz., the 
epithelial, whose only function is to absorb nutritive and 
eliminate waste matters. Thus, by differentiation of 
form and limitation of function, or division of labor, the 


22 WHAT IS EVOLUTION? 


different parts of the organism are bound more and more 
closely together by mutual dependence, and the whole 
becomes more and more distinctly individuated, and 
separation of parts becomes more and more a mutilation, 
and finally becomes impossible without death. This pro- 
cess, as already said, reaches its highest point only in the 
later stages of development of the highest animals. 

Progress.—The law of progress is, of course, admitted 
to be a law of ontogeny ; but observe here, also, it is true 
only of the whole and not necessarily of all the parts, ez- 
cept from the point of view of the whole. ‘Thus, for ex- 
ample, starting all from a common form or generalized 
type, some cells advance to the dignity of brain-cells, 
whose function is somehow connected with the genera- 
tion or at least the manifestation of thought, will, and 
emotion ; other cells descend to the position of kidney- 
cells, whose sole function is the excretion of urine. But 
here, also, the highest cells are successively higher, and 
the whole aggregate is successively nobler and more com- 
plex. It is again a branching and rebranching, in ey- 
ery direction, some going upward, some downward, some 
horizontally, anywhere, everywhere, to increase the com- 
plexity of relations internal and external, and therefore 
to elevate the plane of the whole. 

Cyclical Movement.—Lastly, the law of cyclical move- 
ment is also a law of ontogeny and therefore of evolution. 
This law, however, is less fundamental than the other 
two, and is, therefore, less conspicuous in the ontogenic 
than in the phylogenic series. It is conspicuous only in 


ITS SCOPE AND DEFINITION, 23 


the later stages of ontogeny, and in other higher kinds 
of evolution, such as social evolution. For example, in 
the ontogenic development of the body and mind from 
childhood to manhood we have plainly successive culmi- | 


nations and declines of higher and higher functions. In | 
bodily development we have culminating first the nutri-_ 
tive functions, then the reproductive and muscular, and 
last the cerebral. In mental developmeut we have cul- | 


mination first of the receptive and retentive faculties in - 


soo tn O EME 


childhood, then of imaginative and sesthetic faculties in 
youth and young manhood ; then of the reflective and 
“elaborative faculties—the faculties of productive work in 
mature manhood ; and, finally, the moral and religious 
sentiments in old age. The first gathers and stores ma- ) 
terials; the second vivifies and makes them plastic — 
building materials; the third uses them in actual con- | 
structive work—in building the temple of science and 
philosophy ; and the fourth dedicates that temple only | 
to noblest purposes. ! 

Observe here, also, that when each group of faculties — 
culminates and declines, it does not perish, but only be- | 
comes subordinate to the next higher dominant group, 
and the whole psychical organism becomes not only | 
higher and higher in its highest parts, but also more and | 
more complex in its structure and in the interaction of © 
its correlated parts. 

Observe, again, the necessity laid upon us by this law— © 
the necessity of continued evolution to the end. Child- : 
hood, beautiful childhood, can not remain —it must : 


24. WHAT IS EVOLUTION? 


quickly pass. If, with the decline of its characteristic 
faculties, the next higher group characteristic of youth 
do not increase and become dominant, then the glory of 
life is already past and deterioration begins. Have we 
not all seen sad examples of this? Youth, glorious 
youth, must also pass. If the next higher group of re- 
flective and elaborative faculties do not arise and domi- 
nate, then progressive deterioration of character com- 
mences here—thenceforward the whole nature becomes 
coarse, as we so often See in young men, or else shrivels 
and withers, as we so often see in young women. Final- 
ly, manhood, strong and self-relying manhood, must also’ 
pass. If the moral and religious sentiments have not 
been slowly growing and gathering strength all along, 
and do not now assert their dominance over the whole 
man, then commences the final and saddest decline of 
all, and old age becomes the pitiable thing we so often 
see it, But, if the evolution have been normal through- 
out; if the highest moral and religious nature have been 
gathering strength through all, and now dominates all, 
then the psychic evolution rises to the end—then the 
course of life is like a wave rising and cresting only at 
the moment of its dissolution, or, like the course of the 
sun, if not brightest at least most glorious in its setting. 
And thus—may we not hope ?—the glories of the close of 
a well-spent life become the pledge and harbinger of an 
eternal to-morrow ? : 
We have thus far illustrated the three laws of succes- 
sion of organic forms by ontogeny, because this is the 


— 


ITS SCOPE AND DEFINITION. 95 


type of evolution ; but they may be illustrated also by 
other forms of evolution. Next to the development of 
the individual, undoubtedly the progress of society fur- 
nishes the best illustration of these laws. 

Commencing with a condition in which each indi- 
vidual performs all necessary social functions, but very 
imperfectly ; in which each individual is his own shoe- 
maker and tailor, and house-builder and farmer, and 
therefore all persons are socially alike; as society ad- 
vances, the constituent members-begin to diverge, some 
taking on one social function and some another, until in 
the highest stages of social organization this diversifica- 
tion or division and subdivision of labor reaches its high- 
est point, and each member of the aggregate can do per- 
fectly but one thing. Thus, the social organism becomes 
more and more strongly bound together by mutual de- 
pendence, and separation becomes mutilation. Ido not 
mean to say that this extreme is desirable, but only that 
an approach to this is a natural law of social develop- 
ment. Is not this the law of differentiation ? 

So also progress is here, as in other forms of evo- 
lution—a progress of the whole, but not necessarily of 
every part. Some members of the social aggregate ad- 
vance upward to the dignity of statesmen, philosophers, 
and poets; some advance downward to the position of 
scavengers and sewer-cleansers.* But the highest mem- 
bers are progressively higher, and the whole aggregate is 


* Of course I mean downward in social function, Individually the 
scavenger may be nobler than the statesman. 


26 WHAT IS EVOLUTION ? 


progressively grander and more complex in structure and 
functions. 

So, again, the law of cyclical movement is equally 
conspicuous here. Society everywhere advances, not uni- 
formly, but by successive waves, each higher than the 
last; each urged by a new and higher social force, 
and embodying a new and higher phase of civilization. 
Again: as each phase declines, its characteristic social 
force is not lost, but becomes incorporated into the next 
higher phase as a subordinate principle, and thus the 
social organism as a whole becomes not only higher and 
higher, but also more and more complex in the mutual 
relations of its interacting social forces. 

Let us not be misunderstood, however. There is un- 
doubtedly in social evolution something more and higher 
than we have described, but which does not concern us 
here, except to guard against misconstruction. There 
is in society a voluntary progress wholly different from 
the evolution we have been describing. In ¢rwe or ma- 
terial evolution natural law works for the betterment of 
the whole utterly regardless of the elevation of the indi- 
vidual, and the individual contributes to the advance of 
the whole quite unconsciously while striving only for his 
own betterment. ‘This unconscious evolution by natural 
law inherited from the animal kingdom is conspicuous 
enough in society, especially in its early stages, but we 
would make a great mistake if we imagined, as some do, 

; that this is all. Besides the unconscious evolution by 
natural laws, inherited from below, there is a higher evo- 


ITS SCOPE AND DEFINITION. O71 


° . . f 
lution, inherited from above, indissolubly connected with | 
man’s spiritual nature—a conscious, voluntary striving | 


of the best members of the social aggregate for the bet- / 


terment of the whole—a conscious, voluntary striving | 
both of the individual and of society toward a recog- | 
nized ideal. In the one kind of evolution the fittest | 
are those most in harmony with the environment, and } 
which therefore always survive ; in the other, the fittest \ 


are those most in harmony with the ideal, and which | 


often do not survive. The laws of this free voluntary 


i 


progress are little understood. They are of supreme 
importance, but do not specially concern us here. We | 


will speak of it again in another chapter. 

The three laws above mentioned might be illustrated 
equally well by all other forms of evolution. We have 
selected only those which are most familiar. They may, 
therefore, be truly called the laws of evolution. We 
have shown that they are the laws of succession of or- 
ganic forms. 

III. Change by Means of Resident Forces.—Thus far 
in our argument I suppose that*most well-informed men 
will raise no objection. It will be admitted, I think, 
even by those most bitterly opposed to the theory of evo- 
lution, that there has been throughout the whole geologi- 
cal history of the earth an onward movement of the or- 
ganic kingdom to higher and higher levels. It will be 
admitted, also, that there is a grand and most significant 
resemblance between the course of development of the 
organic kingdom and the course of embryonic develop- 

4 


: 
i 


28 WHAT IS EVOLUTION? 


ment—between the laws of succession of organic forms 
and the laws of ontogenic evolution. But there is an- 
other essential element in ontogenic evolution. It is 
that the forces or causes of evolution are natural ; that 
they reside in the thing developing and in the reacting 
environment. ‘This we know is true of embryonic devel- 
opment; is it true also of the geologic succession of or- 
ganic forms? It is true of ontogeny ; 1s it true also of 
phylogeny ? If not, then only by a metaphor can we call 
the process of change in the organic kingdom throughout 
geological history an evolution. This is the point of 
discussion, and not only of discussion, but, alas ! of 
| heated and even angry dispute. The field of discussion 
is thus narrowed to this third point only. 

Before stating the two opposite views of the cause of 
evolution, it is necessary to remind the reader that when 
the evolutionist speaks of the forces that determine pro- 
gressive changes in organic forms as resident or inherent, 
all that he means, or ought to mean, is that they are 
resident in the same sense as all natural forces are resi- 
dent ; in the same sense that the vital forces of the em- 
bryo are resident in the embryo, or that the forces of the 
development of the solar system according to the nebular 
or any other cosmogonic hypotheses are resident in that 
system. In other words, they mean only that they are 

“) natural, not supernatural. This does not, of course, 
touch that deeper, that deepest of all questions, viz., 
\the essential nature and origin of natural forces ; how 

hea they are independent and self-existent, and how far 


ITS SCOPE AND DEFINITION. 29 


they are only modes of divine energy. This is a question 
of philosophy, not of science. ‘This question is briefly ' 
discussed in another place (Part III, Chap. III) ; it does 
not immediately concern us here. 

The Two Views briefly Contrasted.—As already stated, 
all will admit a grand resemblance between the stages of 
embryonic development and those of the development of 
the organic kingdom. ‘This was first brought out clearly 
by Louis Agassiz, and is, in fact, the greatest result of 
his life-work. All admit, also, that the embryonic de- 
velopment is a natural process. Is the development of 
the organic kingdom also a natural process? All biolo- 
gists of the present day contend that it is; all the old- 
school naturalists, with Agassiz at their head, and all 
anti-evolutionists of every school, contend that it is not. 
We take Agassiz as the type of this school, because he 
has most fully elaborated and most distinctly formulated 
this view. As formulated by him, it has stood in the 
minds of many as an alternative and substitute for evo- 
lution. 

According to the evolutionists, all organic forms, 
whether species, genera, families, orders, classes, ctc., are 
variable, and, if external conditions favor, these varia- 
tions accumulate in one direction and gradually produce 
new forms, the intermediate links being usually destroyed 
or dying out. According to Agassiz, the higher groups, 
such as genera, families, orders, etc., are indeed vari- 
able by the introduction of new species, but species are 
the ultimate elements of classification, and, like the ul- 


30 WHAT IS EVOLUTION ? 


timate elements of chemistry, are unchangeable; and, 
therefore, the speculations of the evolutionist concerning 
the transmutation of spucies are as vain as were the spec- 
ulations of the alchemists concerning the transmutation 
of metals—that the origin of man, for example, from 
any lower species is as impossible as the origin of gold 
from any baser metal. Both sides admit frequent change 
of species during geological history, but one regards the 
change as a change by gradual transmutation of one 
species into another through successive generations and 
by natural process, the other as change by substitution 
of one species for another by direct supernatural creative 
act. Both admit the gradual development of the organic 
kingdom as a whole through stages similar to those of 
embryonic development; but the one regards the whole 
process as natural, and therefore strictly comparable to 
embryonic development, the other as requiring frequent 
special interference of creative energy, and therefore 
comparable rather to the development of a building un- 
der the hand and according to the preconceived plan of 
an architect—a plan, in this case, conceived in eternity 
and carried out consistently through infinite time. It is 
seen that the essential point of difference is this: The 
one asserts the variability of species (if conditions favor, 
and time enough is given) without limit; the other as- 
serts the permanency of specific forms, or their variabil- 
ity only within narrow limits. The one asserts the origin 
of species by ‘‘descent with modifications” ; the other, 
the origin of species by “‘ special act of creation.” The 


ITS SCOPE AND DEFINITION, 31 


one asserts the law of continuity (i. e., that each stage is 
the natural outcome of the immediately preceding stage) 
in this, as in every other department of Nature; the 
other asserts that the law of continuity (i.e., of cause 
and effect) does not hold in this department ; that the 
links of the chain of changes are discontinuous, the con- 
nection between them being intellectual, not physical. 

So much for sharp contrasting characterization of the 
two views, necessary for clear understanding of much 
that follows. We will have to give them more fully 
hereafter when we take up the evidences of evolution in 
Part II. 


CHAPTER II. 


THE RELATION OF LOUIS AGASSIZ TO THE THEORY OF 
EVOLUTION. 


In order to clear up the conception of evolution, it is 
necessary to give a brief history of the idea, and espe- 
cially to explain the relation of Louis Agassiz to that 
theory. ‘This is the more necessary, because there is a 
deep and wide-spread misunderstanding on this subject, 
and thus scant justice has been done our great naturalist, 
especially by the English and Germans ; and also because 
this relation is an admirable illustration of an important 
principle im scientific philosophy. 

Like all great ideas, we find the first germs of this in 
Greek philosophy, in the cosmic speculations of Thales 
and Pythagoras. Next (about 100 B. c.) we find it more 
clearly expressed by the Roman thinker, Lucretius, in 
his great philosophic poem entitled “De Rerum Natura.” 
After a dormancy-of nearly eighteen centuries it next 
emerges with still more clearness in the theological specu- 
lations of Swedenborg and the philosophical speculations 
of Kant. All these we pass over with bare mention, be- 
cause these thinkers approached the subject from the 


RELATION OF AGASSIZ TO EVOLUTION. 83 


philosophic rather than the scientific side—in the meta- 
physical rather than the scientific spirit. 

The first serious attempt at scientific presentation of 
the subject was by the celebrated naturalist, Lamarck, in 
a work entitled ‘‘ Philosophie Zoélogique,” published in 
1809. It is not necessary, in this rapid sketch, to give a 
full account of Lamarck’s views. Suffice it to say that 
the essential idea of evolution, viz., the indefinite vari- 
ability and the derivative origin of species, was insisted 
on with great learning and skill, and illustrated by many 
examples. With Lamarck, the factors of evolution or 
causes of change of organic forms were—1. Modification 
of organs in function and therefore in structure, by a 
changing environment—external factor ; and, 2. Modifi- 
cation of organs by use and disuse—internal factor. In 
both cases the modifications are inherited and increased 
from generation to generation, without limit. This sec- 
ond factor seems to have taken, in the mind of Lamarck, 
the somewhat vague and transcendental form of aspira- 
tion or upward striving of the animal toward higher 
conditions. These are acknowledged to-day as true fac- 
tors of evolution, but the distinctively Darwinian factor, 
viz., ‘‘diyergent variation and natural selection,” was 
not then thought of. The publication of Lamarck’s 
views produced a powerful impression, but only for 
a little while. Pierced by the shafts of ridicule shot 
by nimble wits of Paris, and crushed beneath the 
heavy weight of the authority of Cuvier, the greatest 
naturalist and comparative anatomist of that or perhaps 


34 WHAT IS EVOLUTION? 


of any time, it fell almost still-born. I believe it was 
best that it should thus perish. Its birth was prema- 
ture ; it was not fit to live. The world was not yet pre- 
pared for a true scientific theory. Nevertheless, the 
work was not without its effect upon some of the most 
advanced thinkers of that time; upon Saint-Hilaire and 
Comte in France, and upon Goethe and Oken in Ger- 
many. It was good seed sown and destined to spring up 
and bear fruit in suitable environment ; but not yet. 

The next attempt worthy of attention in this rapid 
sketch is that of Robert Chambers, in a little volume en- 
titled ‘‘ Vestiges of a Natural History of Creation,” pub- 
lished in 1844. It was essentially a reproduction of 
Lamarck’s views ina more popular form. It was not a 
truly scientific work nor written by ascientific man. It 
was rather an appeal from the too technical court of sci- 
ence to the supposed wider and more unprejudiced court 
of popular intelligence. It was therefore far more elo- 
quent than accurate ; far more specious than profound. 
It was, indeed, full of false facts and: inconsequent rea- 
sonings. Nevertheless, it produced a very strong impres- 
sion on the thinking, popular mind. But 7¢ also quickly 
fell, picrced by keen shafts of ridicule, and crushed be- 
neath the heavy weight of the authority of all the most 
prominent naturalists of that time, with Agassiz at their 
head. The question for the time seemed closed. I be- 
heve, again, it was best so, for the time was not yet fully 
ripe. 

I know full well that many think with Haeckel that 


RELATION OF AGASSIZ TO EVOLUTION. So 


biology was kept back half a century by the baneful au- 
thority of Cuvier and Agassiz ; but I can not think so. 
The hypothesis was contrary to the facts of science as 
then known and understood. It was conceived in the 
spirit of baseless speculation, rather than of cautious 
induction ; of skillful elaboration rather than of earnest 
truth-seeking. Its general acceptance would have de- 
bauched the true spirit of science. I repeat it: the time 
was not yet ripe for a scientific theory. The ground 
must first be cleared and a solid foundation built; an in- 
superable obstacle to hearty rational acceptance must 
first be removed, and an inductive Jasis must be laid. 

The Obstacle removed.—The obstacle in the way of 
the acceptance of the derivative origin of species was the 
then prevalent notion concerning the nature of life. We 
must briefly sketch the change which has taken place in 
the last forty years in our ideas on this subject. 

Until about forty years ago, the different forces of 
Nature, such as gravity, electricity, magnetism, light, 
heat, chemical affinity, etc., were supposed to be entirely 
distinct. The realm of Nature was divided up into a 
number of distinct and independent principalities, each 
subject to its own sovereign force and ruled by its own 
petty laws. About that time it began to be evident, and 
is now universally acknowledged, that all these forces are 
but different forms of one, universal, omnipresent energy, 
and are transmutable unto one another back and forth 
without loss. This is the doctrine of correlation of 
forces and conservation of energy, one of the grandest 


36 WHAT IS EVOLUTION? 


ideas of modern times. But one force seemed still to be 
an exception. Life-force was still believed to be a pe- 
culiar, mysterious principle or entity, standing above 
other forces and subordinating them; not correlated 
with, not transmutable unto, nor derivable from, other 
and lower forces, and therefore in some sense super- 
natural. Now, if this be true of living forces, it is per- 
fectly natural, yea, almost necessary, to believe that liv- 
ing forms are wholly different from other forms in their 
origin. New forms of dead matter may be derived, but 
new living forms are wnderived. Other new forms come 
by natural process, new organic forms by supernatural 
process. The conclusion was almost unavoidable. But 
soon vital force also yielded to the general law of correla- 
tion of natural forces. Vital forces are also transmutable 
into and derivable from physical and chemical forces, 
Sun-foree, falling on the green leaves of plants, is ab- 
sorbed and converted into vital force, disappears as light 
to reappear as life. The amount of life-force generated 
is measured by the amount of light extinguished. The 
same is true of animal life. As in the steam-engine the 
locomotive energy is derived from the fuel consumed and 
measured by its amount, so in the animal body, the ani- 
mal heat and animal force are derived from and measured 
by the food and tissue consumed by combustion. Thus, 
vital force may be regarded as so much force withdrawn 
from the general fund of chemical and physical forces, to 
be again refunded without loss at death. This obstacle 
is, therefore, now removed. If vital force falls in the 


RELATION OF AGASSIZ TO EVOLUTION. oF 


same category as other natural forces, there is no reason 
why living forms should not fall into the same category 
in this regard as other natural forms. If new forms of 
dead matter are derived from old forms by modification, 
according to physical laws, there is no reason why new 
living forms should not also be derived from old forms 
by modification according to physiological laws. ‘Thus, 
at last, the obstacle was removed—the ground was 
cleared. 

The Basis laid.—But Science is not content with re- 
moval of a priori objections. She must also have posi- 
tive proofs. The ground must not only be cleared, but a 
true inductive basis of facts, and especially of laws and 
methods, must be laid. Zhis was the life-work of Agas- 
siz. Yes, as strange as it may seem to some, it 1s never- 
theless true that the whole inductive basis, upon which 
was afterward built the modern theory of evolution, was 
laid by Agassiz, although he himself persistently refused 
to build upon it any really scientific superstructure. It 
is plain, then, that all attempts at building previous to 
Agassiz’s work must, of necessity, have resulted in an 
unsubstantial structure—an edifice built on sand, which 
could not and ought not to stand. I must stop here in 
order to explain somewhat fully this important point, 
and thus to give due credit to the work of Agassiz. 

The title of any scientist to greatness must be deter- 
mined, not so much by the multitude of new facts he has 
discovered as by the new laws he has established, and 
especially by the new methods he has inaugurated or per- 


38 WHAT IS EVOLUTION? 


fected, Now, I think it can be shown that to Agassiz, 
more than to any other man, is due the credit of having 
established the laws of succession of living forms in the 
geological history of the earth—laws upon which must 
rest any true theory of evolution. Also, that to him, 
more than to any other man, is due the credit of having 
perfected the method (method of comparison) by the use 
of which alone biological science has advanced so rapidly 
in modern times. This is high praise. I wish to justify 
it. I begin with the method. 

Scientific methods bear the same relation to intellect- 
ual progress that tools, instruments, machines, mechani- 
cal contrivances of all sorts, bear to material progress. 
They are intellectual contrivances—indirect ways of ac- 
complishing results far too hard for bare-handed, unaided 
intellectual strength. As the civilized man has little or 
no advantage over the savage in bare-handed strength of 
muscle, and the enormous superiority of the latter in 
accomplishing material results 1s due wholly to the use 
of mechanical contrivances or machines; even so, in the 
higher sphere of intellect, the scientist makes no preten- 
sion to the possession of greater unaided intellectual 
strength than belongs to the uncultured man, or even 
perhaps to the savage. The amazing intellectual results 
achieved by science are due wholly to the use of intellect- 
ual contrivances or scientific methods. As in the lower 
sphere of material progress the greatest benefactors of 
the race are the inventors or perfecters of new mechani- 
cal contrivances or machines, so also in the higher sphere 


RELATION OF AGASSIZ TO EVOLUTION. 39 


of intellectual progress the greatest benefactors of the 
race are the inventors or perfecters of new intellectual 
contrivances or methods of research. 

To illustrate the power of methods, and the necessity 
of their use, take the case of the method of notation, so 
characteristic of mathematics, and take it even in its 
simplest and most familiar form: Nine numeral figures, 
having each a value of its own, and another dependent 
upon its position; a few letters, a and 0, and ~ and y, 
connected by symbols, + and — and =; that is all. And 
yet, by the use of this simple contrivance, the dullest 
school-boy accomplishes intellectual results which would 
defy the utmost efforts of the unaided strength of the 
greatest genius, And this is only the simplest tool-form 
of this method. Think of the results accomplished by 
the use of the more complex machinery of the higher 
mathematics ! 

Take next the method of experiment so characteristic 
of physics and chemistry. The phenomena of the external 
world are far too complex and far too much affected by 
disturbing forces and modifying conditions to be under- 
_ stood at once by bare, unaided intellectual insight. They 
must first be simplified. The physicist, therefore, con- 
trives artificial phenomena under ideal conditions. He 
removes one complicating condition after another, one 
disturbing cause and then another, watching meanwhile 
the result, until finally the necessary condition and the 
true cause are discovered. On this method rests the 
whole fabric of the physical and chemical sciences. 


40 WHAT IS EVOLUTION? 


But when we rise still higher, viz., into the plane of 
life, the phenomena of Nature become still more com- 
plex and difficult to understand directly ; and yet just 
here, where we are the most powerless without some 
method, our method of experiment almost wholly fazls 
us. ‘The phenomena of life are not only far more com- 
plex than those of dead matter, but the conditions of life 
are so nicely adjusted, the equilibrium of forces so deli- 
cately balanced, that, when we attempt to introduce our 
clumsy hands in the way of experiment, we are in danger 
of overthrowing the equilibrium, of destroying the con- 
ditions of the experiment, viz., life; and then the whole 
problem falls immediately into the domain of chemistry. 
What shall we do? In this dilemma we find that Na- 
ture herself has already prepared for us, ready to hand, 
an elaborate series of simplified conditions equivalent to 
experiments. The phenomena of life are, indeed, far too 
complex to be at once understood—the problem of life 
too hard to be solved—in the higher animals; but, as we 
go down the animal scale, complicating conditions are 
removed one by one, the phenomena of life become sim- 
pler and simpler, until in the lowest microscopic cell or 
spherule of living protoplasm we finally reach the sim- 
plest possible expression of life. The equation of life is 
reduced to its simplest terms, and now, if ever, we begin 
to understand the true value of the unknown quantity. 
This is the natural history series, or Taxonomic series, 
already spoken of on page 10. Again, Nature has pre- 
pared, and is naw preparing daily before our eyes, an- 


RELATION OF AGASSIZ TO EVOLUTION. 41 


other series of gradually simplified conditions. Com- 
mencing with the mature condition of one of the higher 
animals—for example, man—and going backward along 
the line of individual history through the stages of in- 
fant embryo, egg and germ, we find again the phenomena _ 
of life becoming simpler and simpler, until we again 
reach the simplest conceivable condition in the single. 
microscopic cell or spherule of living protoplasm. This, 
as already explained, is the embryonic or Ontogente se- 
ries. Again, that there be no excuse for man’s ignorance 
of the laws of life, Nature has prepared still another 
series; and this the grandest of all, for it is the cause of 
both the others. Commencing with the plants and ani- 
mals of the present epoch, and going back along the 
track of geological times, through Cenozoic, Mesozoic, 
Paleozoic, Eozoic, to the very dawn of life—the first 
syllable of recorded time—and we find again a series of 
organic forms growing simpler and simpler, until, if 
we could find the very first, we would undoubtedly 
again reach the simplest condition in the lowest con- 
ceivable forms of life. This, as we have already seen, 
is the geologic or evolution, or Phylogenic series. We 
have already explained these three series, only in this 
connection it suits our purpose to take the terms back- 
ward. 

Now, it is by comparison of the terms of each of these 
series going up and down, and watching the first appear- 
ance, the growth, and the perfecting of tissues, organs, 
functions, and by the comparison of the three series 


49 WHAT IS EVOLUTION? 


with one another term by term—I say it is wholly by 
comparison of this kind that biology has in recent times 
kecome a true inductive science. This is the ‘‘ method 
of comparison.” It is the great method of research in 
all those departments which can not be readily managed 
by the method of experiment. It has already regenerated 
biology, and is now applied with like success in sociology 
under the name of historic method. Yes; anatomy be- 
came scientific only through comparative anatomy, physi- 
ology through comparative physiology, and embryology 
through comparative embryology. May we not add, soci- 
ology will become truly scientific only through compara- 
tive sociology, and psychology through comparative psy- 
chology ? 

Now, while it is true that this method, like all other 
methods, has been used, from the earliest dawn of 
thought, in a loose and imperfect way, yet it is only in 
very recent times that it has been organized, systema- 
tized, perfected, as a true scientific method, as a great ' 
instrument of research; and the prodigious recent ad- 
vance of biology is due wholly to this cause. Now, 
among the great leaders of this modern movement, Agas- 
siz undoubtedly stands in the very first rank. I must 
try to make this point plain, for it is by no means gen- 
erally understood. 

Cuvier is acknowledged to be the great founder of 
comparative anatomy. He it was that first perfected the 
method of comparison, but comparison only in one series 
—the Taxonomic. Von Baer and Agassiz added to this, 


RELATION OF AGASSIZ TO EVOLUTION, 43 


comparison in the ontogenic series also, and comparison 
of these two series with each other, and therefore the 
application of embryology to the classification of animals. 
If Von Baer was the first announcer, Agassiz was the 
first great practical worker by this method. Last and 
most important of all, in its relation to evolution, Agas- 
siz added comparison in the geologic or phylogenic series. 
The one grand idea underlying Agassiz’s whole life-work 
was the essential identity of the three series, and there- 
fore the light which they must shed on one another. 
The two guiding and animating principles of his scien- 
tific work were—1. That the embryonic development of 
one of the higher representatives of any group repeated 
in a general way the terms of the Taxonomic series in 
the same group, and therefore that embryology furnished 
the key to a true classification ; and, 2. That the succes- 
sion of forms and structure in geological times in any 
group is similar to the succession of forms and struct- 
ure in the development of the individual in the same 
group, and thus that embryology furnishes also the key 
to geological succession. In other words, during his 
whole life, Agassiz insisted that the laws of embryonic 
development (ontogeny) are also the laws of geological 
succession (phylogeny). Surely this is the foundation, 
the only solid foundation, of a true theory of evolution. 
It is true that Agassiz, holding as he did the doctrine 
of permanency of specific types, and therefore rejecting 
the doctrine of the derivative origin of species, did not 


admit the causal or natural relation of phylogenic succes- 
5 


44. WHAT IS EVOLUTION? 


sion to embryonic succession and taxonomic order as we 
now believe it—it is true that for him the relation be- 
tween the three series was an intellectual not a physical 
one—consisted in the preordained plans of the Creator, 
and not in any genetic connection or inherited property ; 
but evidently the first and greatest step was the discovery 
of the relation itself, however accounted for. The rest 
was sure to follow. 

But more. Not only did Agassiz establish the essen- 
tial identity of the geologic and embryonic succession, 
the general similarity of the two series, phylogenic and 
ontogenic, but he also announced and enforced all the 
formal laws of geologic succession (i. e., of evolution), as 
we now know them. These, as already stated and illus- 
trated, are the law of differentiation, the law of progress 
of the whole, and the law of cyclical movement, al- 
though he did not formulate them in these words. No 
true inductive evidence of evolution was possible without 
the knowledge of these laws, and for this knowledge we 
are mainly indebted to Agassiz. He well knew also that 
they were the laws of embryonic development and there- 
fore of evolution ; but he avoided the word evolution, as 
implying the derivative origin of species, and used in- 
stead the word development, though it is hard to see in 
what the words differ. Thus, it is evident that Agassiz 
laid the whole foundation of evolution, solid and broad, 
but refused to build any scientific structure on it; he re- 
fused to recognize the legitimate, the scientifically neces- 
sary outcome of his own work. Nevertheless, without his 


RELATION OF AGASSIZ TO EVOLUTION. 45 


work a scientific theory of evolution would have been 
impossible. Without Agassiz (or his equivalent), there 
would have been no Darwin. 

There is something to us supremely grand in this re- 
fusal of Agassiz to accept the theory of evolution. The 
opportunity to become the leader of modern thought, 
the foremost man of the century, was in his hands, and 
he refused, because his religious, or, perhaps better, his 
philosophic intuitions, forbade. To Agassiz, and, in- 
deed, to all men of that time, to many, alas! even now, 
evolution is materialism. But materialism is Atheism. 
Will some one say, the genuine Truth-seeker follows 
where she seems to lead whatever be the consequences? 
Yes; whatever be the consequences to one’s self, to one’s 
opinions, prejudices, theories, philosophies, but not to 
still more certain truth. Now, to Agassiz, as to all genu- 
ine thinkers, the existence of God, like our own exist- 
ence, is more certain than any scientific theory, than any- 
thing can possibly be made by proof. From his stand- 
point, therefore, he was right in rejecting evolution as 
conflicting with still more certain truth. The mistake 
which he made was in imagining that there was any such 
conflict at all. But this was the universal mistake of the 
age. A lesser man would have seen less clearly the higher 
truth and accepted the lower. A greater man would 
have risen above the age, and seen that there was no 
conflict, and so accepted both. All thinking men are 
coming to this conclusion now, but none had done so 
then, 


46 WHAT IS EVOLUTION? 


Now, then, at last, the obstacle of supernaturalism in 
the realm of Nature having been removed by the estab- 
lishment of the doctrine of correlation of natural forces, 
and the extension of this doctrine to embrace also life- 
force ; and now also a broad and firm basis of carefully- 
observed facts and well-established laws of succession of 
organic forms having been laid by Agassiz, when again, 
for the third time, the doctrine of origin of species ‘‘ by 
derivation with modifications ” was brought forward by 
Darwin in a far more perfect form, with more abundant 
illustrative materials, and with a new and most potent 
factor of modification—viz., divergent variations and 
natural selection—it found the scientific world already 
fully prepared, and anxiously waiting. I say anxiously 
waiting—for the supposed supernatural origin of species 
had been the one exception to the otherwise universal 
law of cause and effect, or the Jaw of continuity. It 
was therefore in open contradiction to the whole drift 
of scientific thought for five hundred years. Is it any 
wonder, then, that the derivative origin of species was 
welcomed with joy by the scientific world? For five 
hundred years, scientific thought, lke a rising tide 
which knows no ebb, had tended thitherward with ever- 
increasing pressure, but kept back by the one supposed 
fact of the supernatural origin of species. Darwin lifted 
the gate, and the in-rushing tide flooded the whole do- 
main of thought. 

What, then, is the place of Agassiz in biological sci- 
ence? What is the relation of Agassiz to Darwin—of 


RELATION OF AGASSIZ TO EVOLUTION. 47 


Agassizian development to Darwinian evolution? I an- 
swer, it ig the relation of formal science to physical or 
causal science. Agassiz advanced biology to the formal 
stage; Darwin carried it forward, to some extent at 
least, to the physical stage. All true inductive sciences 
in their complete development pass through these two 
stages. Science in the one stage treats of the laws of 
phenomena ; in the other, of the causes or explanation of 
these laws. The former must precede the latter, and 
form its foundation ; the latter must follow the former, 
and constitute its completion. The change from the one 
to the other is always attended with prodigious impulse 
to science. 3 

To illustrate: Until Kepler, astronomy was little more 
than an accumulation of disconnected facts concerning 
celestial motions—abundant materials, but no science ; 
piles of brick and stone, but no building. Kepler re- 
duced this chaos to beautiful order and musical harmony 
by the discovery of the three great laws which bear his 
name, and therefore he has been justly called the legis- 
lator of the heavens—the lawgiver of space. But, had 
he been asked the cause of these beautiful laws, he could 
only have answered, ‘‘The first cawse—the direct will 
of the Deity.”” A good answer and a true, but not sci- 
entific ; because it places the question beyond the do- 
main of science, which deals only with second or physical 
causes. But Newton comes forward and gives a physical 
cause. He shows that all these beautiful laws are the 
necessary result of gravitation ; and thus astronomy be- 


48 WHAT IS EVOLUTION ? 


comes a physical science. So, until Agassiz, the facts of 
geological succession of organic forms were in a state of 
lawless confusion. Agassiz by establishing the three great 
laws of succession, which ought to bear his name, re- 
duced this chaos to order and beauty ; and, therefore, he 
might justly be called the legislator of geological history 
—the lawgiver of time. But, when asked the cause of 
these laws, he could only answer, and did indeed an- 
swer, ‘‘'The plans of the Creator.” A noble answer and 
true, but not scientific. Darwin now comes forward and 
gives, partly at least, the cause of these laws. He shows 
that all these beautiful laws are explained by the doc- 
trine of “‘origin of species by derivation with modifica- 
tions”; that these laws are not ultimate, but derivative 
from more fundamental laws of life ; and thus biology is 
advanced one step, at least, toward the causal stage. 
Newton and Darwin substituted second causes for first 
cause—natural for supernatural. They each in his own 
department broke the bonds of supernaturalism in the 
domain of Nature. , 

One more important reflection: There are two, and 
only two, fundamental conditions of material existence— 
space and time. There are, therefore, two, and only two, 
cosmoses — space-cosmos and time-cosmos. These have 
been redeemed from confusion and reduced to law and 
order and beauty—changed from chaos to cosmos—by 
science. For this result we are chiefly indebted, in the 
one case, to Kepler and Newton; in the other, to Agassiz © 
and Darwin. The universal law, in the one cosmos, is 


RELATION OF AGASSIZ TO EVOLUTION. 49 


the law of gravitation ; in the other, the law of evolution. 
Traced by analysis to its deepest roots of philosophic 
truth, the one law may be called the divine mode of sus- 
tentation ; the other, the divine process of creation. 
Or again: we have all heard of the “‘ music of the 
spheres ’—a beautiful and significant name used by the 
old thinkers for the divine order of the universe—a 
music heard not by human ear, but only by the atten- 
tive human spirit. Harmonic relation apprehended by 
reason we call Law, and its embodiment Science; the 
same apprehended by the imagination and esthetic 
sense, we call Beauty, and its embodiment Art, music. 
Now, in music there are two kinds of harmony, simul- 
taneous and consecutive—chordal harmony and melody. 
These must be combined to produce the grandest effect. 
So in cosmic order, too, there are two kinds of harmonic 
relation—the co-existent in space and the consecutive tn 
time. The law of gravitation expresses the universal 
harmonic inter-relation of objects co-existent in space, 
the law of evolution, the universal harmonic relation of 
forms successive in time. Of the divine spheral music, 
the one is the chordal harmony, the other the consecutive 
harmony or melody. Combined they form the divine 
chorus which ‘‘ the morning stars sang together.” 





Pease leek Ls 


EVIDENCES OF THE TRUTH OF 
EHVOLUTION. 





CHAPTER LI. 


GENERAL EVIDENCES OF EVOLUTION AS A UNIVERSAL 
LAW. 


LET us again remind the reader that evolution means, 
first of all, continuity. The law of evolution, although 
it doubtless means much more, means, first of all, a law 
of continuity, or causal relation throughout Nature. It 
means that, alike in every department of Nature, each 
state or condition grew naturally out of the immediately 
preceding. In a word, it means that, in the course of 
Nature, nothing appears suddenly and without natural 
cause, but, on the contrary, everything is the natural and 
usually the gradual outcome of a previous condition. 
This is now admitted by every one in regard to nearly 
everything: evolutionists apply it to the whole course of 
Nature. I said this is now admitted by every one in 
regard to nearly everything; but this has not always 
been so. ‘The world has come to its present position on 
this subject only by a very gradual process. Let us then 
trace rapidly the history of the gradual change, for it 
will prepare us for much that follows. 

There was a time (and that not many decades ago) 


54 EVIDENCES OF THE TRUTH OF EVOLUTION. 


when all things, the origin of which transcends our ordi- 
nary experience, were supposed to have originated sud- 
denly and without natural process—to have been made 
at once, out of hand. ‘There was a time when, for ex- 
ample, mountains were supposed to have been made at 
once, with all their diversified forms, of beetling cliffs and 
thundering waterfalls, or gentle slopes and smiling val- 
leys, just as we now find them. But xow we know that 
they have become so only by a very gradual process, and 
are still changing under our very eyes. In a word, they 
have been formed by a process of evolution. We know 
now the date of mountain-births ; we trace their growth, 
maturity, decay, and death; and find even, as it were, the 
fossil bones of extinct mountains in the crumpled strata 
of their former places. There was a time when continents 
and seas, gulfs, bays, and rivers, were supposed to have 
originated at once, substantially as we now see them. 
Now, we know that they have been changing throughout 
all geological time, and are still changing. Not, however, 
change back and forth in any direction indifferently and 
without goal, but gradual change from less perfect to 
more perfect condition, with more and more complex in- 
ter-relations—i. e., by a process of evolution. We are able 
now, though still imperfectly, to trace some of the stages 
of this evolution. There was a time when rocks and 
soils were supposed to have been always rocks and soils ; 
when soils were regarded as an original clothing made on 
purpose to hide the rocky nakedness of the new-born 
earth. God clothed the earth so, and there an end. Now 


GENERAL EVIDENCES OF EVOLUTION, 5D 


we know that rocks rot down to soils; soils are carried 
down and deposited as sediments; and sediments re- 
consolidate as rocks—the same materials being worked 
over and over again, passing through all these stages 
many times in the history of the earth. In a word, 
there was a time when it was thought that the earth 
with substantially its present form, configuration, and 
climate, was made at once out of hand, as a fit habitation 
for man and animals. Now we know that it has been 
changing, preparing, becoming what it is by a slow pro- 
cess, through a lapse of time so vast that the mind sinks 
exhausted in the attempt to grasp it. It has become 
what it now is by a process of evolution. The same 
change of view has taken place concerning the origin of 
all the heavenly bodies. We may, therefore, confidently 
generalize—we may assert without fear of contradiction 
that all inorganec forms, without exception, have origi- 
nated by a process of evolution. 

The proof of all this we owe to geology—a science 
born of the present century. This science establishes 
the law of universal continuity of events, through infi- 
nite time, as astronomy does that of universal inter-rela- 
tion of objects through infinite space. How great the 
change these two sciences have made in the realm of 
human thought! Until the birth of modern astronomy 
the intellectual space-horizon of the human mind was 
bounded substantially by the dimensions of our earth ; 
sun, moon, and stars, being but ineonsiderable bodies 
circulating at a little distance about the earth, and for 


56 EVIDENCES OF THE TRUTH OF EVOLUTION. 


our behoof. Astronomy was then but the geometry of 
the curious lines traced by these wandering fires on the 
concave blackboard of heaven. With the first glance 
through a telescope the phases of Venus and the satellites 
of Jupiter, revealed clearly to the mind the existence of 
other worlds besides and like our own. In that moment 
the idea of infinite space, full of worlds like our own, was 
for the first time completely realized, and became thence- 
forward the heritage of man. In that moment the inféel- 
lectual horizon of man was infinitely extended. So also 
until the birth of geology, about the beginning of the 
present century, the intellectual fime-horizon of the 
human mind was bounded by six thousand years. The 
discovery about that time of vertebrate remains, all 
wholly different from those now inhabiting the earth, 
revealed the existence of other time-faunas, besides our 
own and the idea of infinite time, of which the life of 
humanity is but an epoch, was born in the mind of 
man; and again the intellectual horizon of man was 
infinitely extended. ‘These two are the grandest ideas, 
and their introduction the grandest epochs, in the intel- 
lectual history of man. We have long ago accepted and 
readjusted our mental furniture to the requirements of 
the one, but the necessary readjustment to the other is 
not yet complete. 

All inorganic forms, then, it is admitted, have come 
by evolution. But how is it with organic or living 
forms? Let us see. 

Every one knows, because it is within the limits 


GENERAL EVIDENCES OF EVOLUTION. 57 


of ordinary experience, that every individual organism 
now originates and gradually becomes what we see it, by 
a natural process—that is, by evolution. If, then, there 
be any exception, it must be only the first of each kind. 
But what kind ? There are many kinds of kinds; classes, 
orders, families, genera, species, varieties. Now, many 
of these kinds can be shown to have become what we see 
them by a gradual process similar, at least, to evolution. 
Take for example, classes. The class of fishes and the 
class of reptiles are now widely distinct and have little in 
common except a vertebrate structure ; but, as already 
shown, page 12, this extreme difference has not always 
existed. On the contrary, the earliest representatives of 
these two classes so merged into one another that each 
seemed either. From this common stock the two classes 
were gradually separated, each going its own way and be- 
coming more and more widely distinct even to the pres- 
ent day. There can be no doubt, therefore, that these two 
classes, a8 we now know them, have become what they are 
by a gradual process. Again: In the whole realm of 
Nature there is not a class more distinctly separate from 
every other and without intermediate links than birds. 
But this has not always been so. They have gradually 
become so. The earliest birds were so reptilian in struct- 
ure and appearance that if we could see them now we 
would be in doubt whether we should call them birds or 
reptiles. Birds have gradually separated themselves from 
the reptilian stem, becoming more and more bird-like 
from age to age, until now, at last, the two classes are 


58 EVIDENCES OF THE TRUTH OF EVOLUTION. 


wholly separated and the intermediate links destroyed. 
So far as external eharacters are concerned, birds may be 
said to have finally and wholly released themselves from 
entangling alliance with any other class. 

Classes, then, it will be admitted, have undoubtedly 
become what we now know them by a very gradual pro- 
cess following laws identical (as we have already seen, 
page 19) with the laws of evolution. Shall we try or- 
ders? Of the class Mammalia there are two well-rec- 
ognized and widely-distinct orders, viz., the Carnivores 
and the Herbivores. We all know how widely diverse 
these are in form, in structure, in habits, and in food. 
Has it always been so? Have these been made so at 
once? By no means. They have gradually become so. 
The earliest mammals were neither the one nor the other 
distinctively. They were omnivores, completely interme- 
diate in food, habits, form, and structure. From this 
common stock the two orders have gradually separated, 
the carnivores becoming more and more adapted to one 
mode of life and the herbivores to another, by a process 
following the laws of evolution, as already explained. 
Shall we try families and genera? Marsh and Huxley 
have shown us how completely the horse family (Hquide) 
and the horse-genus (Hguwus) illustrate the process of 
gradual becoming and the law of evolution. Under their 
guidance, we see that the earliest traceable ancestor of 
the horse family, before it was distinctively a horse fam- 
ily at all, had on the fore-foot five toes in the Lower 
Eocene, four toes in the Upper Eocene, and three toes in 


GENERAL EVIDENCES OF EVOLUTION. = 59 


the Miocene ; then we see the two side-toes shortening up 
more and more in the Pliocene and becoming rudiment- 
ary splints, leaving only one toe in the Quaternary and 
present epochs. Thus, the side-splints in the foot of the 
modern horse tell the story of its three-toed ancestry. 
Similar gradual changes are clearly traceable in size, 
shape, structure of limbs, of teeth, and of brain. In all 
respects the members of the horse family have become 
more and more horse-like in the course of time. 

This subject will be taken up and more fully illus- 
trated, under the head of special evidences, in a subse- 
quent chapter. We here touch it only sufficiently to 
illustrate this universal law of gradual becoming. 

We have taken only a few examples, but the same is 
undoubtedly true of all Taxonomic groups above species. 
Passing over these last for the moment, we take next races 
and varieties. 'These smaller groups are admitted by all 
to be formed by a natural process, because not only can 
we make them artificially, but all the intermediate links 
may be found in Nature. So we have only species re- 
maining. Yes; species are imagined by the old-school 
naturalist and by the anti-evolutionist of to-day as the 
ultimate elements of Taxonomy. ‘This, then, is the last 
ditch upon which the defense of supernaturalism in the 
realm of Nature is made. ‘‘ Other groups,” they say, 
‘‘may have gradually become what they now are by the 
successive introduction of specific forms according to a 
preordained plan which is well expressed by the formal 


laws of evolution. But species are without transition 
6 


60 EVIDENCES OF THE TRUTH OF EVOLUTION. 


forms. They come in suddenly, remain unchanged while 
they continue, and finally pass out suddenly, so far as 
specific characters are concerned. New species come in 
their places by direct act of creation—by substitution, 
not by transmutation.” This, then, is the last intrench- 
ment. Can we give any good evidence of gradual forma- 
tion of species? I believe we can. 

First, then, it is admitted that we can easily make 
varieties and races artificially. We will not now describe 
the process; we are all familiar with the results, viz., 
the varieties of domestic animals and of useful and orna- 
mental plants; the extremely different breeds of horses, 
cattle, sheep, dogs, pigeons, etc. ; of wheat, cabbages, 
turnips; of roses, dahlias, ete., etc. No one will doubt 
that the extreme varieties of any of these, say greyhound 
and pug, if wild, would be called distinct species, or 
even distinct genera. We do not call them so, for two 
reasons: first, because we sce them made; and, second, 
‘because we find all intermediate links between them ; 
and the usual definition of species is. that they can not 
be made, and they have no intermediate links. Thus, 
then, the question is narrowed down to wild species. 
They say: ‘‘ We take our stand on these” (surely a very 
narrow ground for so broad a philosophy). ‘‘ We defy 
you to show gradual formation with intermediate links.” 

Now, in fact, by diligent search such intermediate 
links between well-recognized species have been found in 
some cases, especially in birds, on account of their great 
power of dispersal. Certain forms have long been known 


GENERAL EVIDENCES OF EVOLUTION. 61 


from widely-separated regions, and universally regarded 
as distinct species, as distinct as any. Then, by minute 
examinations of intermediate regions, a complete series of 
intermediate forms has been picked up. ‘This has oc- 
curred not only in one case but in many cases, and not 
in birds only but in many other classes—examples in- 
crease with our increasing knowledge.* ‘The only answer 
to such evidence is that these are not true species. Now, 
see the fallacy lurking here! They define species as ul- 
timate elements of taxonomy, as distinct and without 
intermediate links, and then require us to find such in- 
termediate links; and, finally, when with infinite pains 
some such links are found, they say: ‘‘Oh! I see; we 
were mistaken; they are only varieties!!” It is true 
that naturalists, when intermediate links are found, usu- 
ally put all together as one species, but this they do 
purely for the sake of clearness of definition and descrip- 
tion. It is freely admitted by the evolutionist that spe- 
cies are now usually distinct and without intermediate 
links, these having been destroyed in the struggle for 
life. This will be fully explained in another chapter. 
It is also freely admitted that although intermediate 
links must have existed at one time, their remains are 
rarely found. The reason of this will also be explained 
hereafter. Nevertheless, in some cases, as already seen, 
we do find them still existing. Now, we add that in 
some cases, where they no longer exist, we find them in 


* Cope, “Science,” vol. ii, p. 274, 1883. 


62 EVIDENCES OF THE TRUTH OF EVOLUTION, 


the form of fossil remains. The most remarkable exam- 
ple of this is found in the gradual changes in the forms 
of Planorbis in the fresh-water deposits of Steinheim, as 
shown by the admirable researches of Hyatt.* We shall 
discuss these also more fully in another place. Now, if 
there be any such links at all, however rare, then every 
objection to the derivative origin of species is removed. 

Perhaps it may be well to make bare mention of 
another kind of evidence, viz., the actual change of spe- 
cies under the eyes, by the action of change of environ- 
ment. The different species of the genus Artemia (a low 
form of crustacean) live in brine-pools. By concentrat- 
ing the brine of such a pool, one species (A. salina) has 
been observed to change in successive generations into 
another (A. Muhlhausenii), and the latter back again to 
the former by slow freshening.t Again: The siredon 
and the amblystoma have always, until recently, been re- 
garded as not only distinct species, but distinct genera 
of amphibians. Siredon was supposed to be a permanent 
gill-breather, while amblystoma becomes by metamorpho- 
sis a pure air-breather. Now, however, it is known that 
the former may change into the latter. But the most 
curious part of the life-history of these animals, is that 
if water be abundant the siredon reproduces freely, and 
remains indefinitely a gill-breather; but if the water 
dries up it changes into the lung-breathing amblystoma. 


* Boston Society of Natural History —anniversary memoir, 1880. 
Also, “‘ American Naturalist,” June, 1882. 
+ “ Archives des Sciences,” vol, liv, 1875. 


GENERAL EVIDENCES OF EVOLUTION. 63 


We do not give this as examples of change of species, 
for the change is in the individual life, and therefore in 
the nature of metamorphosis, but as evidence of the 
power of physical conditions in modifying the develop- 
ment of organic forms and therefore of the manner in 
which gill-breathers were probably transformed into air- 
breathers. 

To sum up: 1. All inorganic forms, without excep- 
tion, have become what we find them by a natural pro- 
cess—i. e., by evolution. 2. All organic or living forms 
within the limits of observation, i. e., every living thing, 
has become what we now see, by a gradual, natural pro- 
cess—i. e., by evolution. 3. All taxonomic groups, except 
species, have undoubtedly become what we now see them 
by a gradual process, following the laws of evolution, and 
therefore presumably by a natural process of evolution. 
4, By artificial means, breeds, races, etc., very similar, 
at least in many respects, to species, are seen to arise by a 
gradual natural process—i. e., by evolution. 5. In some 
instances, at least, natural species are observed to pass 
into one another by intermediate links in such wise that 
we are forced to conclude that they have been formed by 
a natural process. 

May we not, then, safely generalize, and make the 
law universal? Is not this a sufficient ground for confi- 
dent induction? Even though some facts are still inex- 
plicable, is that a sufficient reason for withholding assent 
to a theory which explains so much? In all induction 
we first establish a law provisionally from the observation 


64. EVIDENCES OF THE TRUTH OF EVOLUTION. 


of a comparatively few facts, and then extend it overa — 
multitude of facts not included in the original induction. 
If it explains these also, the law is verified. The law of 
gravitation was first based on the observation of a few 
facts, and then verified by its explanation of nearly all 
the facts of celestial motion. There are some outstand- 
ing facts of celestial motion still unexplained, but we do 
not, therefore, doubt the law of gravitation. The same 
principle applied in biology ought to establish the law of 
evolution, for it also explains all the facts of biology as 
no other law can. But inductive evidence differs from 
other kinds of evidence in one respect, which, in fact, 
constitutes its strength to the scientific, but its weakness 
to the popular mind. It is a kind of circumstantial evi- 
dence, but its force does not consist in a few strong cir- 
cumstances easily appreciated, such as strike the popular 
mind, and force conviction, but rather in a multitude of 
small circumstances, each by itself insignificant, but all 
together pointing to one conclusion and demanding one 
explanation. Such evidence is, indeed, overwhelming, 
but only to the mind that masters it. The evidence for 
the law of gravitation is literally the whole science of as- 
tronomy. So also the evidence for the law of evolution is 
the whole science of biology. Neither of these laws can 
be proved in a debating society, but only by a course of 
study. In the one case the law has been universally ac- 
cepted—not, however, on evidence, for there are few in- 
deed who appreciate the evidence, but on the authority 
of scientific unanimity. In the other case there has not 


GENERAL EVIDENCES OF EVOLUTION. 65 


yet been time enough for the already established unanim- 
ity to have its full effect. 

Thus much, we believe, will be generally admitted as 
a very moderate claim. LHvolution is certainly a legiti- 
mate induction from the facts of biology. But we are 
prepared to go much further. We are confident that 
evolution is absolutely certain. Not, indeed, evolution as 
a special theory—Lamarckian, Darwinian, Spencerian— 
for these are all more or less successful modes of explain- 
ing evolution ; nor evolution as a school of thought, with 
its following of disciples—for in this sense it is still in 
the field of discussion—but evolution as a law of deri- 
vation of forms from previous forms ; evolution as a law 
of continuity, as a universal law of becoming. In this 
sense it is not only certain, it is axiomatic. It is only 
necessary to conceive it clearly, to see that it is a neces- 
sary truth. This may seem paradoxical to some. I stop 
to justify it. 

Physical phenomena we all admit follow one another 
in unbroken succession, each derived from a preceding, 
and giving origin to a succeeding. We call this the law 
of causation, and say that it is axiomatic. We might call 
it a law of derivation. So also organic forms follow 
one another in continuous chain, each derived from a 
preceding and giving origin to a succeeding. We call 
this a law of derivation. We might call it a law of causa- 
tion, and say that it too is axiomatic. The origins of 
new phenomena are often obscure, even inexplicable, 
but we never think to doubt that they have a natural 


66 EVIDENCES OF THE TRUTH OF EVOLUTION. 


cause ; for so to doubt is to doubt the validity of reason, 
and the rational constitution of Nature. So also the ori- 
gins of new organic forms may be obscure or even inex- 
plicable, but we ought not on that account to doubt 
that they had a natural cause, and came by a natural 
process ; for so to doubt is also to doubt the validity of 
reason, and the rational constitution of organic Nature. 
The law of evolution is naught else than the scientific or, 
indeed, the rational mode of thinking about the origin of 
things in every department of Nature. Ina word, it is 
naught else than the law of necessary causation applied 
to forms instead of phenomena. Evolution, therefore, is 
no longer a school of thought. The words evolutionism 
and evolutionist ought not any longer to be used, any 
more than gravitationism and gravitationist ; for the law 
of evolution is as certain as the law of gravitation. Nay, 
it is far more certain. The nexus between successive 
events in time (causation) is far more certain than the 
nexus between coexistent objects in space (gravitation). 
The former ts a necessary truth, the latter is usually 
classed as a contingent truth. I have used and may 
continue to use the term evolutionist, but if so it is 
only in deference to the views of many intelligent per- 
sons, who do not yet see the certainty of the law. 


CHAPTER II. 
SPECIAL PROOFS OF EVOLUTION. 
Introductory. 


It will be seen from the preceding chapter that we 
regard the law of evolution in its wider sense, viz., the 
derivative origin of all forms, organic or other, as axio- 
matic, and therefore requiring no further proof. Among 
scientific men there is no longer any discussion of the 
truth of this law, but only of the theories of the causes 
of the law. We believe that to the scientific mind there 
is no other rational mode of looking at the subject of 
origin of organic forms. To such a mind, therefore, all 
that follows is but the deductive application of that law 
in the explanation of the phenomena of organic Nature. 
But it takes time for the popular mind to readjust it- 
self to new and revolutionary truth. Many minds, even 
among the most intelligent, have not yet accepted this as 
the only rational mode of thought. Many men require 
further special proofs of the derivative origin of organic 
forms. Even to those who accept evolution, these proofs 
will be interesting as illustrations of such origin. We 


68 EVIDENCES OF THE TRUTH OF EVOLUTION. 


will attempt to bring out these proofs under several 
heads, the most important of which are: 1. Proofs from 
morphology, or the general laws of animal structure ; 2. 
Proofs from embryology ; 3. Proofs from geographical 
distribution of organic forms; and, 4. Proofs from artifi- 
cial breeding. ‘The subject is so vast that all we can do 
is to touch lightly only the most salient points under 
each of these heads ; for, as we have already said, the evi- 
dence is really nothing less than the whole science of 
biology. Preparatory to this, however, it is necessary to 
bring out a little more fully than before (page 29), 
though still only in outline, the two antagonistic views, 
which may be called the old and the new, or the natural 
and the supernatural, of the origin of new organic forms, 
especially species. 

Origin of New Organic Forms; the Old View briefly 
stated.—According to the old-school naturalists, species 
are the ultimate elements of taxonomy: genera, families, 
orders, etc., may gradually change their character from 
age to age, by the introduction of new species ; but spe- 
cies were supposed to be substantially permanent. It was 
necessary to have some unit for convenience of descrip- 
tion and classification, and this was found to be the best 
because most stable. As in nearly all cases of beliefs, 
this doctrine was held at first somewhat loosely, as a pro- 
visional and convenient view—as a good working hy- 
pothesis—but gradually, under pressure of controversy, 
became more strictly formulated, and, as it were, hard- 
ened into a scientific dogma, especially in the hands of 


SPECIAL PROOFS OF EVOLUTION. 69 


Agassiz. According to this view, the first pair or pairs 
of each specific kind originated we know not how, but 
certainly at once in its present form in full perfection, 
and, therefore, presumably by direct creative act of 
Deity ; and then afterward by the law of generation con- 
tinued to produce others of the same pattern indefinitely. 
Moreover, the first one or more pairs of each kind multi- 
plied and spread abroad in every direction, each from tts 
own center of origin, as far as physical conditions and 
struggle for life with other species would allow. This 
idea explains tolerably well the geographical distribution 
of species as we now find it. For example, species on 
different continents are widely different, because those 
on each have originated independently where we now 
find them, and spread in all directions as far as physical 
conditions would allow, but could not reach other con- 
tinents because of the ocean-barrier. That this is the 
only reason they are not there, is shown by the fact that, 
if they are carried there, they usually do perfectly well. 
Even on the same continent, for the same reason, species 
may be very different if separated by impassable barri- 
ers such as high mountain-chains or by climate. But 
wherever one group of species, originating in one place, 
comes in contact on the margin of their range with 
another group of species originating in another place, 
we see no evidence of transmutation of one form into 
another, but only substitution of one fully-formed spe- 
cies for another equally fully formed. Therefore, we 
must conclude that physical conditions may limit the 


"0 EVIDENCES OF THE TRUTH OF EVOLUTION. | 


range of a species, but can not transmute it into another. 
Thus, to say the least, many of the facts of geographical 
distribution are well explained by this idea of creative 
origin in specific centers and subsequent permanence of 
specific form. We say many of the facts ; we will show 
hereafter that not all can be thus explained. 

But the main question is not of geographical but of 
geological distribution ; not distribution in space, but 
succession in time. Species do not continue forever. On 
the contrary, they have changed many times in the 
course of geological history. As conditions become un- 
favorable, species die out or become extinct, and others 
take their place and carry forward the life and develop- 
ment of the organic kingdom. Now, how do they 
change ? According to this school of thought, here also, 
as in geographical distribution, they are not transmuted 
but replaced; here also physical conditions may destroy 
a species, but can not transform it into another. As spe- 
cies die out, others are created at once, out of hand and 
fully formed in their place; but in accordance with a 
preordained plan consistently carried out and working 
ever toward higher and higher conditions. Thus, life is 
continued on the earth by the alternation of supernatu- 
ral and natural processes ; by the alternate use of direct 
and indirect action of Deity: direct in the introduction 
of first pairs, indirect through the natural process of re- 
production in the continuance and multiplication of the 
species. Each species is made according to a pattern in 
the Divine mind, on a sort of intellectual die, and then 


SPECIAL PROOFS OF EVOLUTION. va 


continues to reproduce a succession of individuals of the 
same pattern as if struck from the same die until the die 
is broken or worn out. Another die is made, of another 
pattern, and individuals are struck from this; and so on, 
throughout the whole geological history of the organic 
kingdom. Only, we must add that the successive dies 
are made to follow one another according to a plan which 
is expressed by the three laws already given on page 11. 
Thus, the origin of individuals is natural, the origin 
of species supernatural ; the making of dies 1s supernatu- 
ral, the coinage is natural. 

We have stated this view in a too extreme form, in 
order to make it clearer. We now, therefore, proceed to 
qualify somewhat. Specific types were held, by writers 
of this school of thought, to be substantially but not 
absolutely unchangeable. Successive individuals of the 
same species were admitted to be not exactly alike. 
Such slight differences were called varieties. It was ad- 
mitted, indeed, that species varied, but it was believed 
that such variations in any direction were strictly limited 
in amount. A species may be compared to a right cyl- 
inder standing on end. As such a cylinder may be tilted 
slightly in one direction or another, without overthrow- 
ing its equilibrium, the cylinder tending ever to right 
itself and return to its origmal position, so a species 
may be varied slightly in one direction or another with- 
out destroying its integrity, the species tending ever to 
return to its normal or typical form. But as the cylin- © 
der, if pushed too far from its normal position, is over- 


72 EVIDENCES OF THE TRUTH OF EVOLUTION. 


thrown, so also a species, if pressed too far in the way of 
variation from its typical form, is destroyed, but not 
changed into another species. As cylinders may be more 
or less rigid, depending upon the breadth of their bases, 
so also some species are more rigidly set in their typical 
form, and some are more plastic to influences causing 
variations, but in all cases there is a limit to the amount 
of oscillation consistent with integrity. 

The New View briefly stated.—According to Darwin, 
and all biologists of the present day, species are variable 
without limit, if only the causes of change are constant and 
slow enough in their operation, and the time long enough. 
A species must be in harmony with its environment, for 
this is the condition of its existence. Now, if the envi- 
ronment change, the species must tend to change slowly 
from generation to generation, so as to readjust its rela- 
tions in harmony with the changing environment. If 
the change of environment be slow, the readjustment 
may be successful, and the species will change gradually 
into another form, so different that it will be called a 
different species, especially if the intermediate gradations 
be destroyed. If the change in the environment be too 
rapid, many species, especially the more rigid, will be 
destroyed, while the more plastic may survive by modifi- 
cation. Thus, at every step in the evolution of the or- 
ganic kingdom, some species have died without issue, 
while others have saved themselves by changing into new 
forms in harmony with the new environment. Compar- 
ing to a growing tree, some branches overshadowed die, 


SPECIAL PROOFS OF EVOLUTION. {3 


while others push on for light, forming new lateral buds, 
and dividing as they grow. By continued divergent 
change species gradually become genera, genera families, 
etc. Thus, varieties, species, genera, families, orders, 
classes, etc., are only different degrees of differences 
formed all in the same way. Varieties are only com- 
mencing species, species commencing genera, and so on. 
There is no making and wearing out of dies, and making 
of new ones; the whole process is a natural one—the 
whole series is genetically connected. In a perfect classi- 
fication varieties, species, genera, families, orders, classes, 
etc., are only different degrees of blood-kinship. 

So much may be regarded as certain, and out of the 
field of discussion among biologists of the present day. 
It is only in defining this process more accurately, and 
especially in the theory of the causes or factors of evolu- 
tion, that there are still difference and discussion. The 
most probable view on this subject we now proceed to 
give. 

Factors of Evolution.—The causes of change or adapt- 
ive modification, or the factors of evolution, are at least 
four well known, and probably many more still un- 
known: 1. The physical environment—heat and cold, 
dryness and moisture—affects function of organs, and 
function affects structure, and both changed function 
and changed structure are inherited by offspring, and 
so increased from generation to generation, becoming 
greater without limit. 2. Increased wse or disuse of 
organs enforced or permitted by change in the environ- 


74. EVIDENCES OF THE TRUTH OF EVOLUTION. 


ment, physical or organic, or both, induces change in 
form, size, and structure of the organs; and this change 
is inherited by the offspring, and so from generation to 
generation small differences are integrated until they be- 
come great without limit. These two factors were recog- 
nized by Lamarck. 3. ‘ Natural selection,” or ‘‘ survival 
of the fittest,” among divergent varieties of offspring. 
This is the distinctive Darwinian factor. In the two 
preceding factors the change is during the individual 
lifetime, and reproduction is supposed to transmit it un- 
changed to the offspring. In this factor, on the con- 
trary, the form and structure are supposed to remain un- 
changed during the individual life, but for some unknown 
cause there are slight variations in different directions 
(divergent) in the offspring from the same parents. 
Now, when we remember that by reproduction the num- 
ber of individuals tends to increase by geometrical pro- 
gression, and that in each generation only a very few (on 
an average only two from all the offspring of one pair) 
can survive, it is evident that among these divergent va- 
rieties those will most likely survive which are most in 
harmony with the external environment, and which pos- 
sess the most efficient organs of defense or of escape, or 
for food-taking. The surviving offspring, therefore, will 
be on the average better in these respects than their par- 
ents. It matters not how little better, for the integration 
of even infinitesimal improvements from generation to 
generation will eventually produce any required amount 
of change. 4. To the above Darwin has added also 


SPECIAL PROOFS OF EVOLUTION. 45 


‘ sexual selection.” In natural selection there is struggle 
of all for food, or means of living. In sexual selection 
there is a struggle among the males for possession of the 
female, and the means of procreation. The one is con- 
nected with the nutritive appetite, the other with the 
reproductive appetite. This mode of selection acts in two 
ways, by the law of battle and the law of attractiveness. 
The strongest or the most attractive males alone, or 
mainly, leaye offspring, which, of course, inherit their 
peculiarities; and these are increased indefinitely by 
integration through successive generations, thus increas- 
ing the strength or the beauty. Of these two laws, the 
law of battle is most conspicuous among mammals, and 
the law of attractiveness among birds. It is evident that 
this factor can not operate among many lower animals 
which are hermaphroditic, nor among plants. 

Of these acknowledged factors of evolution, the first 
two were known to Lamarck and the older evolutionists. 
The third and fourth are distinctively Darwinian. Ac- 
cording to Darwin, while all these are operative, the third 
is the most powerful; but Spencer accords this distinc- 
tion to the Lamarckian factors. Many American zodlo- 
gists take the same view. 

Such until very recently were all the recognized fac- 
tors of evolution. But, within the past year (1886) has 
taken place, it seems to us, the most important advance 
in the theory of evolution since Darwin. It is the sugges- 
tion by Mr. Catchpool, * and afterward the more full elab- 


- 


* “ Nature,” vol, xxxi, p. 4, 1884. 


7 


"6 EVIDENCES OF THE TRUTH OF EVOLUTION. 


oration by Dr. Romanes, of another factor, which he calls 
** physiological selection.” * 

The great objections to the sufficiency of the theory 
of evolution, as left by Darwin, were twofold: 1. While 
natural selection accounts completely for the formation 
of useful structures or adaptive modifications, and 
therefore for differences characterizing classes, orders, 
families, and even genera—for these are all adaptive— 
it can not so completely account for those constitut- 
ing species; for these consist mostly of ¢rivial differ- 
ences in coloration, relative proportion of parts, which 
are of no perceivable use in the struggle for life, and 
therefore could not be preserved and integrated by 
natural selection. Therefore, according to Romanes, 
natural selection is a theory of origin of adaptive struct- 
ures rather than of origin of species. Comparing to a 
growing tree, once admit lateral buds started, and nat- 
ural selection completely accounts for the growth in dif- 
ferent directions, and therefore for the profuse ramifica- 
tion ; but the origin of the lateral buds is not explained. 

2. The second difficulty is as follows: Such com- 
mencing differences as constitute varieties and species 
not only would not be preserved and integrated by nat- 
ural selection unless useful, but would immediately be 
swamped by cross-breeding with the parental form. But, 
as the whole divergence commences in varieties, evi- 


* See abstract of Dr. Romanes’s views, “‘ Nature,” vol. xxxiv, pp. 314, 
836, 862. Also, discussions of the same by Meldola, Galton, Wallace, 
etc., in immediately subsequent numbers, 


SPECIAL PROOFS OF EVOLUTION. (i 


dently it could not commence at all unless this cross- 
breeding be in some way prevented. ‘This may, indeed, 
be done, without the assumption of any new factor of 
evolution, by migration ; and, hence, migration must be 
regarded as an important agent in the creation of new 
forms, not only by the effect of a new environment, but 
also by prevention of the swamping of commencing 
species by cross-breeding with the parental form; but in 
a crowded locality, without outlet for migration (the very 
conditions most favorable for severe competitive strug- 
gle, and therefore for most potent operation of natural 
selection ; and therefore, also, according to Darwin, for 
profuse diversification), commencing varieties could not 
pass into species, because swamped by cross-breeding. 
Once the divergence reaches the point of cross-sterility 
—i. e., of species—then, indeed, by true breeding, charac- 
ters, even though not useful, may be preserved. But 
how is it to commence ? 

This difficulty has been severely felt by all Darwin- 
ists. It seems to us that it is largely met by Dr. Ro- 
manes. According to Romanes, no organ is so subject 
to varietal changes as the reproductive, and these in no 
respect so much as in degrees of fertility. Unfortunate- 


ly, these changes are not visible, and must be judged of . 


only by the results. It is not uncommon, for example, to 
find sterility between individuals (sexual incompatibility) 
who are both of them perfectly fertile with other indi- 
viduals. Similarly, cross-sterility, partial or complete, is 
not uncommon between varieties or races, ag Mr. Darwin 


- 


78 EVIDENCES OF THE TRUTH OF EVOLUTION. 


has long ago noticed. It very generally, as we know, 
occurs between, and, in fact, is constantly used as a test 
of, species. Now, this cross-sterility with parent stock, 
which we find so constant a character of species, and 
which, therefore, must have commenced as a partial cross- 
sterility in varieties, is it antecedent or consequent to 
other variations? It has been usual to suppose it conse- 
quent to a certain amount of divergence, viz., that which 
constitutes, or at least approaches, species. But, accord- 
ing to Romanes, it is antecedent. Among many other 
variations, this is that one which originates species, be- 
cause it prevents reversion by cross- breeding with the 
parent stock, and insures true breeding with its own 
kind. In a word, it sexually isolates the species. Sup- 
pose, then, a species multiplying indefinitely in one lo- 
cality : trivial variations of many kinds, and in many 
directions, occur among the offspring. These are merged 
by cross-breeding into the original type, which, there- 
fore, remains unchanged. But, from time to time, among 
these variations there occur some affecting the reproduc- 
tive organs in such wise as to produce partial or complete 
cross-sterility with the parent form. This is the begin- 
ning of a new species. It breeds true with its own kind, 
and therefore all the associated variations external and 
visible, and therefore constituting species, although triv- 
ial and of no use in the struggle for life, are preserved. 

This view completely accounts for the cross-fertility 
of artificial breeds equivalent in other respects to species ; 
for cross-sterility is not an end aimed at by the breeder, 


SPECIAL PROOFS OF EVOLUTION. 9 


it being easy to prevent cross-breeding, if desired, by 
artificial isolation. But, if this view be true, species 
from widely-different geographical regions ought also to 
be often cross-fertile, because, having been formed by 
geographical isolation, sexual isolation was not a neces- 
sary factor in their formation. ‘This point deserves test- 
ing by careful observation. 

It may be, and has been, objected to Dr. Romanes’s 
claims, that this is no new factor; that physiological 
selection is only a form of natural selection. ‘This objec- 
tion, it seems to us, is little more than a play upon 
words. It certainly is selection, and by a natural pro- 
cess, and therefore in some sense a natural selection, but 
not in the sense of Darwin. It is not a selection of indi- 
viduals fittest to survive ; for cross-fertile individuals are 
as fit to survive as individuals, though not as species, as 
are cross-sterile. Natural selection is intent only on pre- 
serving the best individuals; physiological selection on 
preserving the kind. Natural selection continues the 
direction of progress unchanged; physiological makes 
new directions. 

In addition to all these factors of organic evolution, 
there is still another far higher factor characteristic of 
man alone. This is the conscious, voluntary co-operation 
of the thing evolving—the spirit of man—in the work of 
its own evolution. ‘This may be called the rational factor. 
This, the most important factor of human evolution, is 
usually ignored by writers on evolution—either as non- 
existent, or else as lying beyond the domain of science. 


80 EVIDENCES OF THE TRUTH OF EVOLUTION. 


We will emphasize its importance by taking it up more 
fully in the next chapter. 

It will be observed that Darwin and his followers take 
divergent variations of offspring simply as a known fact, 
upon which natural selection operates to produce pro- 
gressive modification; and, as the cause of variation in 
offspring is wholly unknown, such variations are often 
spoken of as fortuitous. But, of course, it is well under- 
stood that nothing in Nature is really fortuitous. They 
may, however, for all purposes of natural selection be 
thus regarded until we know their cause. It is evident, 
then, that if we, with Darwin, take natural selection, as 
the most important known factor, the really most impor- 
tant cause of evolution is the cause of varieties. This is 
the wnknown fundamental factor. As Darwin reduced 
Agassiz’s three formal laws of succession to more general 
laws of life, and thus made one important step in the 
advance of biological science, so he who shall explain the 
cause of divergent variation will make another important 
step by reducing the phenomena to still more general 
and fundamental laws of life. 

In conclusion, let me again impress upon the reader 
that all the doubt and discussion, above described, as to 
the factors of evolution, is entirely aside from the truth 
of evolution itself, concerning which there is no differ- 
ence of opinion among thinkers. 


CHAPTER III. 


THE GRADES OF THE FACTORS OF EVOLUTION AND THE 
ORDER OF THEIR APPEARANCE. 


WE have given in the previous chapter six factors of 
evolution—viz.: 1. Pressure of the environment. 2. Use 
and disuse of parts. 3. Natural selection. 4. Sexual 
selection. 5. Physiological selection. 6. Reason. Let 
us now compare these as to their grade in the scale of 
energy and as to the order of their introduction. 

The first two or the Lamarckian factors are the low- 
est in position, the most fundamental and universal, and 
therefore the first in the order of appearance. They pre- 
cede all other factors, and were doubtless for a long time 
the only ones in operation. For, observe, all the selective 
factors—i. e., those of Darwin and Romanes—are condi- 
tioned on reproduction ; for the changes produced by these 
are not in the individual during life, but in the offspring 
at birth. And not only so, but the operations of these fac- 
tors are further conditioned on sexwal modes of reproduc- 
tion; for all the non-sexual modes of reproduction—as, 
for example, by fissure and by budding—are but slight 
modifications of growth, and the resulting multitude of 


89 EVIDENCES OF THE TRUTH OF EVOLUTION. 


organisms may be regarded as in some sense only an ex- 
tension of the first individual. Of course, therefore, the 
identical characters of the first individual are continued 
indefinitely, except in so far as they are modified in suc- 
cessive generations by the effect of the environment and 
by use and disuse—i.e., by the Lamarckian factors. In 
sexual generation, on the contrary, the characters of two 
diverse individuals are funded in a common offspring; 
and the same continuing through successive generations, 
it is evident that the inheritance in each individual off- 
spring is infinitely multiple. Now, the tendency to varia- 
tion in offspring 7s in proportion to the multiplicity of 
the inheritance: for among the infinite number of slight- 
ly differing characters, as it were, offered for inheritance 
in each generation, some individuals will inherit more of 
one and some more of another character. In a word, 
sexual reproduction by multiple inheritance fends to varia- 
tion of offspring, and thus furnishes material for natural 
selection.* 

Thus, then, I repeat, all the selective factors are ab- 
solutely dependent on sexual modes of reproduction. 
But there was a time when this mode of reproduction 
did not yet exist.t The sexual modes developed out of 
non-sexual modes. If these non-sexual preceded sexual 
modes of reproduction, it is evident that at first only 
Lamarckian factors could operate. Evolution was then 


* This subject is more fully treated in chapter IX, p. 240 et seq. 
+ See an article entitled “Genesis of Sex,” “Popular Science 
Monthly,” 1879, vol. xvi, p. 167. 


THE GRADES OF THE FACTORS OF EVOLUTION. 83 


carried forward wholly by changes in the individual pro- 
duced by environment and by use and disuse (acquired 
characters), inherited and increased by integration 
through successive generations indefinitely. It is prob- 
able, therefore, that the rate of evolution was at first 
comparatively slow; unless, indeed, as seems probable, the 
earliest forms were then and the lowest forms are now 
more plastic under the influence of physical conditions 
than are the present higher forms. Doubtless, now, in 
the higher animals and plants, the Darwinian factors are 
by far the most potent; for,among plants, where we can 
use these factors separately,if we wish to make varieties, 
we propagate by seeds (sexual reproduction) ; but, if we 
wish to preserve varieties, we propagate by buds and cut- 
tings (non-sexual reproduction). 

I have taken the two Lamarckian factors together, 
and showed that they preceded the Darwinian. But even 
in the two Lamarckian factors there is a difference in 
grade. Undoubtedly the lowest, the most fundamental, 
and therefore the first introduced, was pressure of the 
physical environment. For use and disuse of organs 
implies some degree of volition and voluntary motion, 
and therefore already some advance in the scale of evo- 
lution. 

With the introduction of sex another entirely differ- 
ent and higher factor was introduced, viz., natural selec- 
tion, or selection of the fittest individuals of a varying 
progeny. We have already seen how sexual generation 
produces variation of offspring, and how this furnishes 


84 EVIDENCES OF THE TRUTH OF EVOLUTION, 


materials for natural selection. As soon, therefore, as 
this form of generation was evolved, this higher factor 
came into operation and immediately assumed control ; 
while the previous factors became subordinate, though 
still underlying, conditioning, and modifying the activity 
of the higher. ‘The result was an immediate increase in 
the rate of evolution. It is very worthy of note that it 
is in the higher animals, such as birds and mammals, in 
which we have only the highest forms of sexual repro- 
duction, where the diversity of characters of the two 
sexes funded in the offspring is the greatest, and where, 
therefore, the variation in offspring is also greatest and 
natural selection most active; it is precisely among these 
that the Lamarckian factors are most feeble, because, 
during the most plastic period of life, the offspring is 
removed from the influence of the physical environment, 
and from use and disuse by its inclosure within the 
womb, or within a large egg surrounded with abundant 
nutriment. Development is already well advanced before 
Lamarckian factors can operate at all. 

Next, I suppose, physiological selection, or Romanes’s 
factor, came into operation. After the introduction of 
sex, 1t became necessary that the individuals of some 
varieties should be isolated in some way, so as to prevent 
the swamping of varietal characters, as fast as formed, in 
a common stock, by cross-breeding. In very low forms, 
with slow locomotion, such isolation might easily take 
place accidentally. Even in higher forms, changes in 
physical geography or accidental dispersion by winds and 


THE GRADES OF THE FACTORS OF EVOLUTION. 85 


currents would often produce geographical isolation, and 
thus, by preventing crossing with the parent stock, secure 
the formation of new species from such isolated varieties. 
But, in order to insure in all cases the preservation of 
commencing species, sexwal isolation, or partial or com- 
plete infertility of some varieties with other varieties and 
with the parent stock, was introduced, as I suppose, later. 
The process by which this takes place has already been 
explained. According to Romanes, natural selection 
alone, with cross-breeding, tends to monotypal evolution ; 
isolation of some kind is necessary for polytypal evolu- 
‘tion. The tree of evolution, under the influence of nat- 
ural selection alone, grows, palm-like, from its terminal 
bud ; isolation of varieties was necessary for the starting 
of lateral buds, and thus for the profuse ramification 
which is its most conspicuous character. 

Next, I suppose, was introduced sexwal selec or 
contest among the males, by battle or by display, for pos- 
session of the females, and the success of the strongest or 
the most attractive; and the perpetuation and increase of 
these superior qualities of strength and beauty in the 
next generation. This, I suppose, was later, because con- 
nected with a higher development of the psychical na- 
ture. This is especially true where splendor of color or 
beauty of song determines the selection. As might be 
supposed, therefore, this factor is operative only among 
the highest animals, especially birds and mammals.* 





* Mr. Wallace has recently, in his work on “Darwinism,” taken 
strong ground against this Darwinian factor. He thinks, for example, 


86 EVIDENCES OF THE TRUTH OF EVOLUTION. 


Next and last, and only with the appearance of Man, 
another entirely different and far higher factor was intro- 
duced, viz., conscious, voluntary co-operation in the work 
of his own evolution—a conscious, voluntary striving to 
attain an ideal. We have called this a factor, but it is 
much more than a mere factor, co-ordinate with other 
factors. It is, rather, a different kind of evolution. It is 
evolution on a higher plane and by another nature. As 
physical Nature works wneonsciously, using certain fac- 
tors, so spirt¢wal nature works consciously, co-operating 
and using the same factors. At first this factor, if we 
still call it so, was extremely feeble. In the early stages 
of his progress, man, like other animals, was largely 
urged on by forces of organic evolution, unknowing and 
uncaring whither he tended. But more and more, as 
civilization advances, this higher and distinctively human 
factor becomes more and more dominant, until now, in 
civilized communities, it takes control of evolution. 
Reason, instead of Nature, now assumes control, though 
still using the methods and factorsof Nature. This free, 
self-determined evolution of the race, in order to distin- 
guish it from the necessary evolution of the organic 
kingdom, we call progress. 

Now, in this whole process we observe two striking 


that sexual vigor is the cause of both the splendor of color and the 
pertinacity which secures the female. We see little difference in this 
way of putting it. Our object, however, is not to argue the question 
of what are true factors, but simply to give the most accepted, and, 
as it seems to us, also the most probable view. 


THE GRADES OF THE FACTORS OF EVOLUTION. 87 


stages. The one is the introduction of sex, the other is 
the introduction of reason.* ‘They may be compared to 
two equally striking stages in the development of the 
individual. As the ontogenic evolution receives fresh 
impulse at the moment of fertilization, so the evolution of 
the organic kingdom receives fresh impulse at the mo- 
ment of introduction of sex. As in ontogenic evolution 
the individual at birth enters upon a new and higher 
plane, in which it co-operates in its own physical growth, 
so the organic kingdom, with the introduction of man, 
enters upon a new and higher plane, in which man co- 
operates in the physical and spiriéwal growth of the race. 
With sex three new and higher factors were introduced, 
and these immediately assumed control and quickened 
the rate of evolution. With reason another and infinitely 
higher factor is introduced, which, in its turn, assumes 
control, and not only again quickens the rate, but ele- 
vates the whole plane of evolution. Moreover, this volun- 
tary, rational factor not only takes control itself, but 
transforms all other factors and uses them in a new way 
and for its own higher purposes. 

This last is by far the greatest change which has ever 
occurred in the history of evolution. In organic evolu- 


* By reason I mean the faculty of dealing with the phenomena of 
the inner world of consciousness and ideas. Animals live in one world 
—the outer world of sense; man in two—the outer world of sense, 
like animals, but also in an inner and higher world of ideas, All that 
is characteristic of man comes of this capacity of dealing with the 
inner world. In default of a better word I call it reason. If any one 
can suggest a better word, I will gladly adopt it. 


§8 EVIDENCES OF THE TRUTH OF EVOLUTION. 


tion Nature operates by necessary law without the con- 
scious voluntary co-operation of the thing evolving. In 
human progress man voluntarily co-operates with Nature 
in the work of evolution, and even assumes to take the pro- 
cess mainly into his own hands. Organic evolution is by 
necessary law, human progress by free or at least by freer 
law. Organic evolution is by a pushing upward and 
onward from below and behind, human progress by a 
drawing upward and onward from above and in front by 
the attractive force of ideals. In a word, organic evolution 
is by the law of force, human evolution by the law of love. 

It may be weil to stop a moment and show briefly 
some of the differences between organic and human evo- 
Iution—differences which are, of course, wholly the result 
of the introduction of this new factor: 

1. In organic evolution “ the fittest” are those most in 
harmony with the physical environment, and therefore 
they survive. In human evolution the fittest are those 
most in harmony with ¢he ideal, and often, especially in 
the early stages, when the race is still largely under the 
dominion of organic factors, they do not survive, because 
not in harmony with the social environment. But, al- 
though the fittest individuals may indeed perish, the ideal 
survives in the race and will eventually triumph. 

2. In organic evolution the weak, the sick, the help- 
less, the unfit in any way perish and ought to perish, be- 
cause this is the most efficient way of strengthening the 
blood or physical nature of the species, and thus of carry- 
ing forward evolution. In human evolution the weak, 





THE GRADES OF THE FAOTORS OF EVOLUTION. g9 


the helpless, the sick, the old, the unfit in any way are 
sustained and ought to be sustained, because sympathy, 
love, pity, strengthen the spirié or moral nature of the 
race. But let us remember that in this material world of 
ours and during this earthly life the spirit or moral nature 
is conditioned on the physical nature; and, therefore, in 
all our attempts to help the weak we must be careful to 
avoid poisoning the blood and weakening the physical 
vigor of the race by inheritance. This gravest of social 
problems, viz., How shall we obey the higher law of love 
and mutual help without weakening the dlood of the race 
by inheritance and the spirit of the race by removing the 
necessity of self-help ?—this problem, I believe, can and 
will be solved by a rational education, physical, mental, 
and moral. I onlyallude to this. It is too wide a field to 
follow up here. 

3. In organic evolution the bodily form and structure 
must continually change in order to keep in harmony 
with the ever-changing environment. In other words, 
organic evolution is by continual change of species, 
genera, families, etc. There must be continual evolution 
of new forms by modification. In human evolution, on 
the contrary, and more and more as civilization advances, 
man modifies the environment so as to bring it into har- 
mony with himself and his wants, and therefore there is no 
necessity of change of bodily form and structure or mak- 
ing of new species of man. Human evolution is not by 
modification of form—new species; but by modification of 
spirit—new planes of activity, higher character. And the 


90 EVIDENCES OF THE TRUTH OF EVOLUTION, 


spirit is modified and character elevated, not by pressure 
of an external physical environment, but by the attractive 
force of an internal spiritual ideal. 

4. The way of evolution toward the highest—i. e., from 
protozoan to man and from lowest man to the ideal, the 
divine man—is a very straight and narrow way, and few 
there be that find it. In the case of organic evolution it 
is so straight and so narrow that any divergence there- 
from is fatal to upward movement toward man. Once 
get off the track, and it is zmpossible to get on again. No 
living form of animal is on its way manward, or can by 
any possibility develop into man. They are all gone out 
of the way. There is none going right; no, not one. 
The organic kingdom developing through all geological 
times may be compared to a tree whose trunk is deeply 
buried in the lowest strata, whose great limbs were sepa- 
rated in early geological times, whose secondary branches 
diverged in middle geological times, and whose extreme 
twiglets, and also its graceful foliage, its beautiful flowers, 
and luscious fruits, are the fauna and flora of the present . 
day. But this tree of evolution is an excurrent stem, con- 
tinuous through the clustering branches to the terminal 
shoot—man. Once leave the stem as a branch, and it is 
easy to continue growing in the direction chosen, but 1m- 
possible to get back on the straight upward way to the high- 
est. In human evolution, whether individual or racial, the 
same law holds, but with a difference. If individual or 
race gets off the straight, narrow way toward the highest 
—the divine ideal—it is hard, very hard to get back on 


THE GRADES OF THE FACTORS OF EVOLUTION. 91 


the track. Hard, I say, but not impossible, because 
man’s conscious voluntary effort is the chief factor in his 
own evolution. By virtue of self-activity, through the 
use of reason and co-operation in the work of evolution, 
man alone of all created things is able to rectify an error 
of direction and return again to the deserted way. 

5. In organic evolution, when a higher factor appears, 
it immediately assumes control, and previous lower factors 
sink into a subordinate position, though still underlying 
and conditioning the higher. But in human evolution, 
the higher rational factor, when it comes in with man, 
not only assumes control, but transforms all other factors 
and uses them in a new way and for its own higher pur- 
poses. In fact, as already said, it is much more than a 
mere factor. It determines a new kind of evolution— 
evolution on a new and higher plane, though, indeed, 
underlaid and conditioned by the laws of organic evolu- 
tion. As external physical Nature uses many factors to 
carry forward organic evolution, so the internal spiritual 
nature, characteristic of man alone, uses these same fac- 
tors in a new way to carry forward human evolution or 
progress. ‘Thus, for example, one organic factor—the en- 
vironment—is modified or even totally changed so as to 
effect suitably the human organism. This is hygiene. 
Again, use and disuse—another factor—is similarly trans- 
formed. The various organs of the body and faculties of the 
mind are deliberately used in such wise and degree (deter- 
mined by reason) as to produce the highest efficiency of 


each part and the greatest strength and beauty of the whole. 
8 


92 EVIDENCES OF THE TRUTH OF EVOLUTION. 


This is education—physical, mental, moral. So also the 
selective factors are similarly transformed, and natural 
selection becomes rational selection. We all know how 
this method is applied to domestic animals and cultivated 
plants in the formation of useful or beautiful varieties. 
Why should it not be applied also to the improvement of 
our race in the selection of our mates in marriage, or in 
the selection of our teachers, our law-makers, our rulers? 
Alas! how little even yet does reason control our selection 
in these matters! How largely are we yet under the 
law of organic evolution ! 

Application of these principles to some questions of 
the day: 

I. Evolution, as a law of derivation of organic forms 
from previous forms by descent with modifications, as 
already shown, is as certain as the law of gravitation. 
This question has passed beyond the realm of doubtful 
discussion; but the causes, the factors, the details of the 
process of evolution are still under discussion. Both 
Darwin and Spencer, the two great founders of the 
theory of evolution in its modern form, acknowledge 
and insist on at least four factors, viz., the two la- 
marckian and the two distinctively Darwinian. The 
only difference between them is in the relative impor- 
tance of the two sets: Spencer regarding the former and 
Darwin the latter as the more potent. But in these 
latest times there has arisen a class of biologists, includ- 
ing some of highest rank, such as Wallace, Weismann, 
and Lankester, who out-Darwin Darwin himself in their 


THE GRADES OF THE FACTORS OF EVOLUTION. 93 


exaltation of the most distinctive Darwinian factor, viz., 
natural selection. They try to show that natural selec- 
tion is the sole and sufficient cause of evolution; that 
changes in the individual, whether as the effect of the 
environment or by use and disuse of organs, are not in- 
herited at all; that Lamarck was wholly wrong; that 
Darwin (in connection with Wallace) was the sole founder 
of the true theory of evolution; and, finally, that Darwin 
himself was wrong only in making any terms whatever 
with Lamarck. This view has been called Neo-Dar- 
wintsm. 

Perhaps the reasons for this view have been most 
strongly put by Weismann, and are based partly on experi- 
ments, but mainly on his ingenious and now celebrated 
theory of the immortality of germ-plasm. The animal 
body consists of two kinds of cells wholly different in 
function—somatic cells and germ-cells, including in this 
last the sexual elements both male and female. Somatic 
cells are specially modified for the various functions of 
_ the body; germ-cells are wholly unmodified. The so- 
matic cells are for the conservation of the zndividual life, 
the germ-cells for the conservation of the species. In the 
development of the egg the germ-cell multiplies itself 
into a cell-aggregate, and then most of the resulting mul- 
titude of cells are modified in various ways to form the 
tissues and organs of the body—somatic cells; but a few 
are reserved and put aside in an unmodified form in the 
sexual organs as germ-cells, to again produce ova which 
again divide into somatic and germ cells, and so on in- 


94 EVIDENCES OF THE TRUTH OF EVOLUTION, 


definitely. Now, according to Weismann, inheritance is 
only through germ-cells, while the environment affects 
only the somatic cells. Therefore changes produced by 
the environment can not be inherited. Sexual modes of 
generation were introduced for the purpose of producing 
variability in progeny, and thus furnishing material for 
natural selection, as this was the only means of evolu- 
tionary advance. Weismann made many experiments on 
animals, especially by mutilation, to show that somatic 
changes are not inherited. 

A full discussion of this question would be unsuitable 
in a work like this. We will therefore content ourselves 
with making three brief remarks: 

a. If the views presented in the early part of this 
chapter are true, then the Lamarckian factors must be 
true factors, because there was a time when there were no 
others. ‘They were therefore necessary, at least to start 
the process, even if no longer necessary at present. 

6. But if these factors were ever operative, they must 
be so still, though possibly in a subordinate degree. A 
lower factor is not abolished, but only becomes subordi- 
nate to a higher when the latter is introduced. Thus it 
may well be that Lamarckian factors are comparatively 
feeble at the present time and among living species, 
especially of the higher animals, and yet not absent alto- 
gether. In the earliest stages of evolution there was a 
complete identification of germ-cells and somatic cells—of 
the individual with the species. In such cases, of course, 
any effect of the environment must be inherited and in- 


THE GRADES OF THE FACTORS OF EVOLUTION. 95 


creased from generation to generation. But the differen- 
tiation of the germ and somatic cells was not all at once, 
nor is their sympathetic relation completely severed. It 
was a gradual process, and therefore the effect of the 
environment on the germ-cells through the somatic cells 
continued, though in decreasing degree, and still contin- 
ues. The differentiation in the higher animals is now 
so complete that germ-cells are probably not at all af- 
fected by changes in somatic cells, unless these changes 
are long continued in the same direction, and are not 
antagonized by natural selection. 

c. It is a general principle of evolution that the law 
of the whole is repeated with modifications in the part. 
This is a necessary consequence of the unity of Nature. 
We ought to expect, therefore, and do find, that the order 
of the use of the factors of evolution is the same in the 
evolution of the organic kingdom, in the evolution of 
each species, and in the evolution of each individual. In 
all these the physical factors are at first. powerfully opera- 
tive; these become subordinate to organic factors, and 
these, in their turn, to psychical and rational factors. 
Therefore, as the individual in its early stages—i.e., in 
embryo and infancy—is peculiarly plastic under the influ- 
ence of the physical environment, and afterward becomes 
more and more independent of these; so a species when 
first formed is more plastic under the influences of La- 
marckian factors, and afterward becomes more rigid to 
the same. And so also the organic kingdom was at first 
more plastic under Lamarckian factors, and has become 


96 EVIDENCES OF THE TRUTH OF EVOLUTION. 


less so in the present species, especially in the higher ani- 
mals. ‘The principal reason of this, as we have already 
seen, is the increasing differentiation of germ and so- 
matic cells, and the removal of the former to the interior, 
where they are more and more protected from external 
influence. | 

II. Some evolutionists—the materialistic—insist on 
making human evolution identical in all respects with 
organic evolution. This, we have shown, is not true. 
The very least that can be said is that a new and far 
more potent factor is introduced with man, which modi- 
fies greatly the process. But we may claim much more, 
viz., that evolution is here on a different and higher 
plane. The factors of organic evolution are, indeed, still 
present, and condition the whole process; but they are 
not left to be used by Nature alone. On the contrary, 
they are used in a new way and for higher purposes—by 
reason. 

But by a revulsion from the materialistic extreme 
some have gone to the opposite extreme. They would 
place human progress and organic evolution in violent 
antagonism, as if subject to entirely different and even 
opposite laws; but we have also shown that, although the 
distinctive human factor is indeed dominant, yet it is 
underlaid and conditioned by all the lower factors; that 
these lower factors are still necessary as the agents used 
by reason. 

III. We have already given the views of Weismann 
and Wallace, and some reasons for not accepting them; 


THE GRADES OF THE FACTORS OF EVOLUTION. 97 


but there is one important aspect not yet touched. There 
are some logical consequences of these views when applied 
to human evolution which seem to us nothing less than a 
reductio ad absurdum. This brings into view still another 
contrast between organic evolution and human progress. 

In organic evolution, when the struggle for life is 
fierce and pitiless as it is now among the higher animals, 
natural selection is undoubtedly by far the most potent 
factor. It is at least conceivable (though not probable) 
that at the present time organic evolution might be car- 
ried on mainly or even wholly by this factor alone; but 
in human evolution, especially in civilized communities, 
this is impossible. If Weismann and Wallace be right, 
then alas for all our hopes of race improvement—phys- 
ical, mental, and moral !—for natural selection will never 
be applied by man to himself as it is by Nature to organ- 
isms. His spiritual nature forbids. Reason may freely 
use the Lamarckian factors of environment and of use 
and disuse, but is debarred the unscrupulous use of natu- 
ral selection as its only method. As this is an important 
point, we must explain. 

All enlightened schemes of physical culture and hy- 
giene, although directed primarily to secure the strength, 
the health, and the happiness of the present generation, 
yet are sustained and ennobled by the conviction that the 
improvement of the individuals of each generation enters 
by inheritance into the gradual physical improvement of 
the race. All our schemes of education, intellectual and 
moral, though certainly intended mainly for the improve- 


98 EVIDENCES OF THE TRUTH OF EVOLUTION. 


ment of the individual, are glorified by the hope that the 
race also is thereby gradually elevated. It is true that 
these hopes are usually extravagant; it is true that the 
whole improvement of one generation is not carried over 
by inheritance into the next; it is true, therefore, that we 
can not by education raise a lower race up to the plane of 
a higher in a few generations or even in a few centuries: 
but there must be at least a small residuum, be it ever so 
small, carried forward from each generation to the next, 
which, accumulating from age to age, determines the slow 
evolution of the race Such are the hopes on which all 
noble efforts for race-improvement are founded. Are all 
these hopes baseless? ‘They are so if Weismann and 
Wallace are right. If it be true that reason must direct 
the course of human progress, and if it be true also that 
selection of the fittest in the organic sense is the only 
method which can be used by reason, then the dreadful 
law of pitiless destruction of the weak, the helpless, the 
sick, the old, must with Spartan firmness be voluntarily 
and deliberately carried out. Against such a course we 
instinctively revolt with horror, because contrary to the 
law of our spiritual nature. 

But the use by reason of the Lamarckian factors is 
not attended with any such revolting consequences. All 
our hopes of race-improvement, therefore, are strictly con- 
ditioned on the efficacy of these factors—i. e., on the fact 
that useful changes, determined by education in each gen- 
eration, are to some extent inherited and accumulated in 
the race. . 


CHAPTER IV. 


SPECIAL PROOFS, TAKEN FROM THE GENERAL LAWS OF 
ANIMAL STRUCTURE, OR FROM COMPARISON IN 
THE TAXONOMIC SERIES. 


General Principles. 


Analogy and Homology.—In biology those organs or 
parts in different animals are said to be analogous which, 
however different their origin, have a general similarity 
of form and especially of function ; while those are called 
homologous which, however different their general ap- 
pearance, and however different their function, yet may, 
by close examination and extensive comparison, be shown 
to be modifications of one another—to be, in fact, origi- 
nally the same part modified for different purposes. In 
the former the parts compared look and behave as if they 
were the same, but are not; in the latter they look and 
behave entirely differently, but are, in fact, the same 
part in disguise. 

We can best make this plain by examples. The wing 
of a bird and the wing of a butterfly are analogous or- 
gans. ‘They have the same function—i. e., flying; and 
this function necessitates the same general form of a flat 


100 EVIDENCES OF THE TRUTH OF EVOLUTION. 


plane. But they are not at all homologous ; they are not 
at all the same organ or part. They certainly have never 
been formed one out of the other by modification. But 
the wing of a bird, the fore-paw of a reptile or mammal, 
the wing of a bat, and the arm and hand of a man, 
though so different in form and function, are homologous 
parts. On close examination they are found to have the 
same general structure, to be composed of essentially the 
same pieces, although they are so greatly modified in or- 
der to adapt them to different functions, that the general 
or superficial resemblance is now lost. ‘Their structure is 
precisely such as it would be if they had all originated 
from some archetypal fore-limb by modifications in dif- 
ferent directions of its several parts. By extensive com- 
parison in the taxonomic and ontogenic series, all the 
intermediate gradations between these extreme modifica- 
tions may be picked up. 

Another example. The lungs of a mammal and the 
gills of a fish are analogous organs, since they have the 
same function of aération of the blood. But they are 
not at all homologous: they are not built on the same 
plan; by no effort of the mind can we imagine that the 
former could have come out of the latter by modifica- 
tion. On the contrary, we have positive proof that it 
did not socome. But there is an organ in the fish which 
is homologous with the mammalian lung, viz., the air- 
bladder, or swim-bladder. We know it—l. Because we 
can trace in the taxonomic series all the gradations from 
the one to the other. In most fishes the air-bladder is 


SPECIAL PROOFS. 101 


wholly cut off from the gullet, and only very feebly sup- 
plied with blood. It is used and can be used only for 
flotation. In others, as the gar-pike, the swim-bladder 
is quite vascular and opens by a tube into the throat. 
Through this opening air is gulped down from time to 
time into the bladder, and again from time to time ex- 
pelled. In other words, this fish supplements its gill- 
breathing by an imperfect lung-breathing. We have here 
the beginning of a lung. In still other fishes, viz., the 
Dipnoi (lepidosiren and ceratodus, Fig. 2), the air-blad- 





Fig. 2.—Lepidosiren. 


der becomes a more perfect lung—i. e., a very vascular 
sacculated sac; and there is not only an opening into 
the throat, but also from the throat to the snout. In 
other words, we have for the first time nostrils. These 
fishes completely combine gill-breathing with lung- 
breathing. The step from these to the lowest am- 
phibian reptiles is so small, that some have classed the 
lepidosiren among amphibians instead of fishes. The 
siredon or axolotl of New Mexico, the necturus or meno- 
branchus of our Northern lakes, and the siren of our 
Southern swamps, have both gills and lungs, and breathe 
both air and water; but the lung is very imperfect, being 
only a sacculated sac, like the air-bladder of the cerato- 


102 EVIDENCES OF THE TRUTH OF EVOLUTION. 


dus and lepidosiren. No one doubts that the air-breath- 
ing organ of an amphibian is a true lung; yet we have 
traced all the gradations between it and the air-bladder 
of afish. We conclude, therefore, that if there be any 
such thing as transmutation of organic forms, the lung 
of higher animals must have been formed by the process 
above described.* 

But we know it still more certainly—2. Because we 
can trace the change from the one to the other in the on- 
togenic series. In the life-history of the individual we 
can actually see the one thing change into the other. The 
frog, as is well known, when first hatched, is a tadpole. 
It has no legs, but locomotes by means of a vertically- 
expanded tail. It has no lungs, but breathes water in- 
stead of air, by means of gills. It is in all respects, 
therefore, a fish, and would be classed as such if it re- 
mained in this condition. But it does not; it gradually 
loses its tail and gills, and acquires legs and lungs, and 
breathes air only. Now in this change whence came the 
lungs? From the gills by modification? No; but 
from an organ similar in character and position to the 
air-bladder of a ceratodus, or a lepidosiren. ‘This organ 
has gradually developed into alung. The steps of the 
change are briefly as follow: First, the breathing is 
wholly water-breathing by gills. Next, by the develop- 
ment of this other organ, it is partly water-breathing by 


* While all comparative anatomists agree that the lung is a diver- 
ticulum from the cesophagus, like the air-bladder of the gar-fish, some 
think that it is a different diverticulum, which is seen first in the dipnoi. 


SPECIAL PROOFS. 103 


gills, and partly air-breathing by lungs. Lastly, the gills 
gradually dry up, and the Jungs develop more and more, 
until the breathing is wholly by lungs. 

We have dwelt somewhat upon this example, because 
it is an excellent example of what we mean by homology, 
and also because we will have occasion to use it again. 
But so important, for all that follows in this part, is a 
clear idea on the subject of homology, that it will be best 
to familiarize the mind of the reader with it by means 
of a few examples drawn from plants. 

A potato is analogous to a root—a tuberous root like 
that of a dahlia or a sweet-potato—but is not at all ho- 
mologous with these. On the contrary, it is homologous 
with a stem. It is essentially an underground, leafless 
branch, which has thickened enormously at the point by 
accumulation of starch. The evidence of this is found 
in the fact that it has rudimentary leaves (scales) ar- 
ranged in regular spiral order of phylotaxis, each with 
its axillary bud (eyes). It is still more clearly shown by 
the fact that buds above-ground which, if let alone, 
would form leafy branches, may be made to become tu- 
bers by covering them with earth or dead leaves, and 
thus excluding the hght; and, conversely, underground 
buds which, if let alone, would form tubers, may be 
made to grow into leafy branches by exposing them to 
the light. 

Take another example: The broad, flat, elliptical, 
green masses so characteristic of the cactus family, and 
usually called their leaves, are indeed analogous to leaves 


104 EVIDENCES OF THE TRUTH OF EVOLUTION. 


in color, form, and function; for they are green and 
fiat, and assimilate carbonic acid and water (CO, and 
H,O) like leaves. But they are not, in truth, leaves, 
but modified stems, for they have the essential structure 
of stems, with their pith, wood, medullary rays, and 
bark, and may be traced through all gradations into 
the ordinary cylindrical form of stems. Where are their 
leaves, then? Their spines are their abortive leaves. 
These are arranged spirally like leaves, and bear buds 
in their axils lke leaves. They are, in truth, leaves, 
modified to perform the function of defensive armor ; 
while their function has been delegated to the stem 
flattened for this purpose. 

One more example: The acacias, of which there are 
fifteen to twenty species in California, introduced from 
Australia, form two groups haying extremely different 
styles of leaves. We will call them the feather-leaved 
and the simple-leaved acacias. In the former, the leaves 
are very finely bipinnate, and the general aspect of the 
foliage is extremely feathery and graceful. In the latter 
the leaves are simple, ovate, and, curiously enough, set 
on edge; and the general aspect of the tree is therefore 
rather stiff. It seems at first incredible that leaves so 
different and aspects so diverse should belong to plants 
of the same genus. But a little close examination shows 
that, as usual, the botanists are right and the popular 
judgment wrong. The plumose-leaf is the normal leaf- 
form for this genus. The simple leaf is not only abnor- 
mal, but in a homological sense is not a leaf at all—i. e., 


SPEOIAL PROOES. 105 


it does not correspond to the part called the blade in 
ordinary simple leaves of other trees. In the seedling of 
_ the simple-leaved acacias, and sometimes for a consider- 
able time in the young tree, the leaves are all plumose. 
As the tree matures it gradually changes its dress and 
puts on its toga virilis. The gradual change from the 


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B32 Ze Tag 
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Fig. 3.—A branch of young acacia, showing change from one form of 
leaf to the other; a, b, ¢, d, successive stages of change; @, s, leaf 
stalk which gradually changes into the blade in ¢, d, and e. 


one form to the other may easily be traced in the same 
tree, and even often in the same branch (Fig. 3). The 


106 EVIDENCES OF THE TRUTH OF EVOLUTION. 


steps of the change (a, 0, c, and d) are shown in the fol- 
lowing figure, drawn from nature. It is seen, by bare in- 
spection of the figure, that the so-called leaf, d, of the 
simple-leaved acacias, is really the vertically-expanded 
leaf-stalk, 7, s, the true leaf or blade being wholly aborted. 
The whole structure of this so-called leaf is different 
from that of a true blade. For example, its style of rib- 
bing is parallel, its position is edgewise to the sky, its 
palisade cells are on both sides alike, etc. ‘To empha- 
size this difference, botanists call such an apparent leaf a 
phyllodium, or phyllode. 

After these illustrations we now repeat the defini- 
tions in different words. Analogy has reference to 
general resemblance of form determined by similarity 
of function, however different the origins of the parts 
compared may be. Homology has reference to com- 
munity of origin, however obscured to the superficial 
observer such common origin may be by modifications 
necessary to adapt to different functions. Observe, — 
then, there are two ideas here which must be kept 
distinct. One is common origin, always shown by 
deep-lying, essential identity of structure; the other 
is adaptive modification for function. Organs of the 
most diverse origin may resemble by adaptive modifi- 
cation for the same function. This is analogy. Or- 
gans of the same origin may assume very different 
appearance by adaptive modifications for different func- 
tions. This is homology. In the latter case, which is 
the one that concerns us, a profound study of essential 


SPECIAL PROOFS. 107 


structure and structural relations to other parts, and 
especially extensive comparison in the taxonomic and 
ontogenic series, will usually detect the homology, or 
common origin, in spite of the obscurations produced by 
adaptive modifications. It is seen, also, that analogy is 
a superficial resemblance, easily detected by the popular 
eye, and therefore embodied in popular language ; while 
homology is a deep-seated and essential resemblance, 
detected often only by profound study and extensive 
comparison. Now, one of the strongest proofs of the 
truth of evolution is taken from the homologies of ani- 
mal structure. Common origin completely explains 
homology. Every other explanation is transcendental, 
and therefore unscientific. 

Primary Divisions of the Animal Kingdom.—Now, 
the animal kingdom consists of several primary divisions, 
called sub-kingdoms or departments. The animals in 
these groups differ so essentially from one another in their 
plan of structure, that it is difficult, if not impossible, to 
trace any structural relation between them—to imagine 
how the members of one could have been derived from 
those of another—or conceive the common stem from 
which they all separated. In other words, it is impos- 
sible, in the present state of knowledge, to trace ho- 
mology with any certainty from one group to an- 
other. But within the limits of each primary group 
the homology is easy. Some naturalists—Agassiz and 
Cuvier—have made four or five of these primary groups. 


Some—Huxley—have made eight. Some make nine or 
9 


108 EVIDENCES OF THE TRUTH OF EVOLUTION. 


ten.* We will not trouble ourselves to settle this ques- 
tion ; for all agree to make vertebrata and articulata or 
arthropoda two of them, and all our illustrations will be 
drawn from these. Other groups are too unfamiliar to 
the general reader to serve our purpose. 

Now, as already stated, homology can not be traced 
with any certainty between the primary groups, but 
within the limits of each group it may be traced with 
ease and beauty. Analogy, however, being connected 
with function, and function being universal, can be 
traced throughout the animal kingdom. While, there- 
fore, it is probable, nay, almost certain, that all animals 
have had acommon origin, we can not yet trace these 
great departments by homology to that common origin. 
But the common origin of each department is quite clear. 
For example, the structure of all vertebrate animals is 
precisely such as would be the case if all came from one 
primal vertebrate, variously modified to adapt to vari- 
ous modes of life. Also, the structure of all arthropods 
is precisely such as would be if all came from one primal 
arthropod, which, from generation to generation, be- 
came gradually modified in different directions, in order 
to adapt itself to various modes of life. But between 


* Undoubtedly the true principle on which primary groups ought to 
be made is, identity of general plan of structure, or traceableness of ho- 
mology throughout. For these groups are the great primary branches of 
the tree of life, and classification ought to represent degrees of genetic 
relationship. This was Agassiz’s principle, although he did not admit the 
genetic relation. This principle has been, it seems to us, too much neg- 
lected by later systematists, 


SPECIAL PROOFS. 109 


arthropods and vertebrates we can not yet clearly see a 
common origin, although there doubtless was such. 
These great departments may, therefore, be compared 
to natural styles of animal architecture. As there are 
various styles of human architecture—Oriental, Egyp- 
tian, Greek, Gothic—each of which may be variously 
modified to adapt it to all the different purposes for 
which buildings are made, without destroying, though 
perhaps obscuring, the integrity of the style; so the dif- 
ferent primary groups or departments may be regarded 
as different styles of animal structure, each of which 
may be and has been modified in many ways to adapt it 
to various habits and modes of life, obscuring but not 
destroying the general style. Or they may be compared 
to natural machines. As a steam-engine, by modifica- 
tion, may be adapted to many kinds of purposes, obscur- 
ing, perhaps, but not destroying the essential identity of 
structure ; even so the vertebrate machine by modifica- 
tion may be, and has been, adapted to many kinds of 
purposes, and thus become a swimming-machine, a 
crawling-machine, a flying-machine, a running- and leap- 
ing-machine, without destroying, although obscuring, 
the essential identity of structure. As in architecture, 
esthetic principles of form may be traced through each 
style, but not from style to style, while the mechanical 
principles of construction run through all alike; so 
also in animal architecture, the laws of form and styles 
of structure are traceable with ease only within the 
limits of each primary group, while the laws of function 


110 EVIDENCES OF THE TRUTH OF EVOLUTION. 


are traceable through all groups alike. Or, again, and 
finally : Each of these departments may be compared to 
a tree, with branches, twigs, and spray, all obviously 
coming from one common stem, but each stem seems 
separate. ‘They are, indeed, probably, themselves only 
great branches of one common trunk, but their connec- 
tion is too remote and obscure to be made out clearly by 
means of homology. Other evidences, however, drawn 
from other sources, as we shall see hereafter, are not 
wholly wanting. 


1 


CHAPTER V. 


PROOFS FROM HOMOLOGIES OF THE VERTEBRATE 
SKELETON, 


THE proposition to be established here is, that all ver- 
tebrates have not only a common general plan of struct- 
ure, but an essential identity even in detail, although 
this identity is obscured by adaptive modifications. We 
will try to show first a common general plan, and then, 
taking parts most familiar to the general reader, will 
show essential identity even in detail. 

Common General Plan.—1. All vertebrate animals, and 
none other, have an internal jointed skeleton worked by 
muscles on the outside. As we shall see hereafter, the 
relation of skeleton and muscle in arthropods is exactly 
the reverse. 

2. In all vertebrates, and in none other, the axis of 
this skeleton is a jointed backbone (vertebral column) 
inclosing and protecting the nervous centers (cerebro- 
spinal axis). These, therefore, may well be called back- 
boned animals. 

3. All vertebrates, and none other, have a number of 
their anterior vertebral joints enlarged and consolidated 


112 EVIDENCES OF THE TRUTH OF EVOLUTION. 


into a box to form the skull,* in order to inclose and pro- 
tect a similar enlargement of the nervous center, viz., the 
brain ; and also usually, but not always, a number of pos- 
terior joints, enlarged and consolidated to form the pel- 
vis, to serve as a firm support to the hind-limbs. 

4, All vertebrates, and none other, have two cavities, 
inclosed and protected by the skeleton, viz., the neural 
cavity above, and the visceral or body cavity below, the 
vertebral column ; so that a cross-section of the body is 
diagrammatically represented by Fig. 4. 

5. All vertebrates, with few ex- 
ceptions, and no other animals, have 
two and only two pair of limbs. 
The exceptions are of two kinds, 
viz. : a, some lowest fishes, amphi- 
oxus and lampreys, which probably 
represent the vertebrate condition 
before limbs were acquired ; and 3, 
degenerate forms like snakes and 
some lizards, which have lost their 
Fic. 4.—Diagram cross- limbs by disuse. 

section through the 

body of a vertebrate, So much concerns the general 

2 ele Fp ccna plan of skeletal structures, and is 

soba. Mi eee strongly suggestive of—in fact, is 


cavity; c,centrumof inexplicable without—common ori- 
vertebra. 





gin. But much more remains 
which is not only suggestive, but demonstrative of such 
origin. By extensive comparison in the taxonomic and 





* The Amphioxus, the lowest of all vertebrates—if vertebrate it may 
be called—is an exception to 2 and 8. In this animal the vertebrate 
type is not yet fully declared. 


PROOFS FROM HOMOLOGIES. 1138 


ontogenic series, the whole vertebrate structure in all its 
details in different animals may be shown to be modi- 
fications one of another. Sometimes a piece is enlarged, - 
sometimes diminished, or even becomes obsolete ; some- 
times several pieces are consolidated into one ; but, in spite 
of all these obscurations, corresponding parts may usually 
be made out. This is the main subject of this chapter. 

Special Homology of Vertebrate Limbs.—It would 
lead us much too far into unfamiliar technicalities to 
take up the whole skeleton. We select the limbs, both 
because their general structure is more familiar, and be- 
cause in them the two fundamental ideas of essential 
identity and of adaptive modification are both admirably 
illustrated. The reason of this is, that it is by the limbs 
that the organism chiefly reacts on the environment, and 
is modified by it. 

Fore-limbs.—In the accompanying figures (Figs. 5- 
18) we have represented, side by side, the fore-limbs of 
many vertebrates, taken from all the classes—mammals, 
birds, reptiles, and fishes. For convenience of compari- 
son, the corresponding parts are similarly lettered in all. 
Also, in order to identify easily certain important corre- 
sponding segments, we have drawn through them a con- 
tinuous dotted line. In man, nearly all the parts are 
present, and his limbs, therefore, may be taken as a term 
of comparison ; for man’s structure, except his brain, is 
far less modified than that of many animals. 

Note, then, the following points: 1. The collar-bone 
(clavicle) is associated with wide separation of the shoul- 
ders, and the free use of the fore-limb for prehension or 





114 EVIDENCES OF THE TRUTH OF EVOLUTION. 


for flight, but is gradually lost in proportion as the fore- 
limb is brought nearer together and used for support, 





aie oe ee 
[--- enn G 
se, scapula ; 


8. Sheep. 9. Horse. 


7. Hog. 
c, coracoid ; a,4, two bones of fore-arm, (Taken from various sources and grouped.) 


6. Dog. 


Figs. 5-9.—5. Fore-limb of man. 


because it is no longer wanted. I say graduaily, for all 
the steps of the passing away may be found. The use- 
less rudimentary condition is not uncommon. 


PROOFS FROM HOMOLOGIES, 115 


2. The coracoid (c), it is seen, is a small, beak-like 
process of the blade-bone (scapula) in man and mam- 
mals ; but in birds (Fig. 11) and reptiles (Figs. 14, 18) 





Fia. 10. Fie. 11; Fig, 12. Fia. 138. 


Figs. 10-13.—10. Fore-limb of bat. 11. Bird. 12. Archeopteryx. 13. 
Pterodactyl. (Lettered as in previous figures ; grouped from various 
sources. ) 


it is a separate bone as large as the blade-bone itself, 
jointed with the latter at the shoulder and with the 
breast-bone (sternum) in front, thus making together a 
strong shoulder-girdle for the attachment of the fore- 
limb. This was undoubtedly the condition in the origi- 
nal or earliest walking animal, viz., reptiles. It was 
inherited and retained by birds, because necessary for 
powerful action of the wings in flight. In mammals it 
gradually dwindled and became united with the blade- 
bone as a process. In one mammal, the lowest and most 


116 EVIDENCES OF THE TRUTH OF EVOLUTION. 


reptilian living—the ornithorhynchus—the coracoid is 
much like that of reptiles—a large, flat bone, separated 
from the blade-bone and articulated with the breast- 





Fig. 14. Wie, 15. Fra. 16. Fia. 17, 
Fias. 14-17.—14. Fore-limb of turtle. 15. Mole. 16. Whale. 14, Fish. 


bone. It is a significant fact that, in the mammalian 
embryo, it is first developed as a separate bone and 
afterward united with the scapula. 

3. In man, monkeys, bears, and some other mam- 
mals, the limb is fairly free from the body and the el- 
bow half-way down the limb ; while in herbivores (Figs. 
8, 9), such as the horse, ox, and deer, etc., the elbow is 
high on the side of the body, and the limb is free only 
from the elbow downward. Perhaps in these cases most 
observers do not recognize it as an elbow at all. All 
gradations between these extremes are easily traced. 
The free condition of the limb is evidently the original 
one, the condition in herbivores being an extreme modi- 


PROOFS FROM HOMOLOGIES. ghiys 


fication associated with another modification mentioned 
under 5. 

4, In man and in many mammals, and in all reptiles 
and birds, there are two bones in the forearm (radius 
and ulna). In the more spe- 
cialized forms of hoofed animals 
(ungulates), such as horse and 
ruminants (Figs. 8, 9), there is 
apparently but one. Two is the 
normal and original number ; 
but one of them, the ulna, has 
gradually become smaller and 
smaller, and finally is reduced 
to a short splint, and consoli- 
dated with the radius as a pro- 
cess extending backward to form 
the point of the elbow. In the 
horse family every step of this 


Fic, 18.—Mosasaur. 


reduction and consolidation may 
be traced in the course of its 
zeological history. 

5. The wrist of many mam- 
mals and all birds differs in 
structure from that of man, 
chiefly in containing a smaller 
number of bones. The normal 
number, as in man, seems to be 





eight. The decrease takes place 
mainly by consolidation of two or more intoone. Insuch 


118 EVIDENCES OF THE TRUTH OF EVOLUTION. 


cases usually the embryo will show the bones still separate, 
thus revealing the ancestral condition. Again, the posi- 
tion of the wrist is noteworthy. In man, monkeys, the 
bear family, and several other mammalian families, and 
in all reptiles, the hand bends forward at the wrist, so 
that the tread is on the whole palm (palmigrade). But, 
in all the most specialized mammals, the wrist can not 
bend in this direction, and therefore this joint can not be 
brought to the ground. ‘The tread is therefore on the 
toes (digitigrade), and the wrist is high up above the 
ground. In the horse (Fig. 9), the ox, and many other 
mammals, for example, the wrist is so high that it is 
not usually recognized as a wrist, and is often called 
the fore-knee. Now, homologous parts ought to have 
the same scientific name; but to use the word ‘‘hand” 
in the case of lower animals might produce confusion 
and misconception. Therefore it has been agreed among 
comparative anatomists to use instead the Latin word 
“manus” for all that corresponds, in any animal, to 
the hand of man—i. e., all from the wrist downward. 
The manus of a horse is about fifteen inches long. The 
manus of a pterodactyl, such as that found by Marsh 
in the cretaceous strata of the West, with an expanse 
of wings of twenty-five feet, was probably not less than 
seven or eight feet long. 

6. The number of palm-bones (metapodal) and toes 
deserves special notice. In fishes, and in some extinct 
swimming reptiles, these are or were very numerous, but 
in the earliest land-animals they became five. This is 


PROOFS FROM HOMOLOGIES. 119 


the number now in nearly all reptiles, and in all the 
more generalized mammals. It may be called the normal 
number for a walking animal. In very many mammals, 
such, for example, as the dog family, they are reduced to 
four, though the fifth often remains as a useless, rudi- 
mentary splint and dew-claw (Fig. 6), thus showing the 
process of dwindling in the ancestry. In hoofed ani- 
mals the precess of gradual diminution is shown even 
in existing forms, and still better in extinct forms. 
Confining ourselves, now, only to existing forms, in the 
elephant there are five palm-bones and toes, and in the 
hippopotamus there are four, all functional. In the hog 
(Fig. 7) there are still four, but two are behind the 
others and much smaller, and do not touch the ground 
—are not functional unless in soft ground. In the cow, 
deer, etc., the palm-bones are reduced to two, and these 
are consolidated into one (canon-bone), and the toes are 
reduced to two efficient and two useless rudiments. In 
the sheep and the goat (Fig. 8) these useless rudiments 
are dropped, and there are two only. finally, in the 
horse (Fig. 9), the ¢ees are reduced to one, although the 
palm-bones are still three, two of them, however, being 
reduced to rudimentary splints. 

How is it with birds? MHave these also palm-bones 
and fingers? Yes, in birds (Fig. 11) there are three 
palm-bones and three fingers (the fourth and fifth being 
wanting) ; one of them—the thumb—is free, and some- 
times carries a claw. In the earliest known and most 
reptilian bird, the archzopteryx (Fig. 12), all the three 


120 EVIDENCES OF THE TRUTH OF EVOLUTION. 


fingers are free, have the full number of joints, and all 
of them carry claws. In the embryo of living birds the 





Fig, 19.—Restoration of Rhamphorhynchus phyllurus (after Marsh). One-seventh nat- 
ural size 


fingers are all free, as 
in the archsegpteryx. 
%. Observe, finally, 
as an admirable illus- 
tration of different 
adaptative modifica- 
tions for the same pur- 
pose — flight — the 
structure of the manus 
of flying animals. In 
the bat (Fig. 10), the 
flat flying - plane is 
made by enormous 
elongation of the palm- 
bones and finger-bones, 
their wide separation 
and the stretching of 
a thin membrane be- 
tween them. In the 
pterosaurs, or extinct 
flying reptiles (Fig. 
13), one finger only is 
greatly enlarged and 


elongated, and the flying-membrane is stretched between 
it and the hind-leg (Fig. 19), while the other three fingers 


are free and provided with claws. 


If it be asked which 


finger is it that is so greatly enlarged in this animal, 


PROOFS FROM HOMOLOGIES. 121 


we answer, it is the ttle finger. In birds, on the con- 
trary, the manus is consolidated to the last degree, to 
form a strong basis for attachments for the quills which 
form the flying-plane, and which are themselves extreme 
modifications of the scales of reptiles. But throughout 
all these extreme modifications the same essential struct- 
ure is detectable. 

It is perhaps unnecessary to dwell upon the still 
greater modifications of limbs for swimming, as in the 
whale (Fig. 16), the ichthyosaur, mosasaur (Fig. 18), 
and the fish (Fig. 17). A careful inspection of the 
figures, after what we have said, will be sufficient to 
explain them. In the fish alone the upper segments of 
the limb, viz., shoulder-girdle and humerus, are want- 
ing, not being yet introduced, and the manus is not 
yet differentiated into palm-bones and fingers, and the 
fingers are indefinitely multiplied. All these characters 
are indications of low position in the scale of evolu- 
tion. The earliest vertebrates were fishes. Limbs were 
not yet completely formed. In embryos of higher ani- 
mals, also, the outer segments are first formed. 

Hind-Limbs. —Figs. 20 to 24 represent, in a similar 
way, the hind-limbs of several animals—in this case all 
mammals. As before, corresponding parts are similarly 
lettered, and a dotted line is carried through certain 
prominent parts, especially the knee, heel, instep, and 
toes. By careful inspection the figures explain them- 
selves. Nevertheless, it will be well to draw special at- 
tention to several of the more important points: 





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PROOFS FROM HOMOLOGIES. 123 


the knee is far removed and half-way down the limb 
(Figs. 20, 21). This is undoubtedly the original and 
normal condition of Jland-animals. But in all the more 
highly specialized and swifter animals the knee is brought 
nearer and nearer to the body, until, in the swiftest of 
all, such as the ruminants and the horse (Figs. 23, 24), 
it is high up on the side of the body, in the middle of 
what is usually called the thigh but which really includes 
the thigh and the upper part of the lower leg or shank. 

2. See, again, the position of the heel. In man, 
monkey, bear, and many other mammals, and all living 
reptiles, the heel is on the ground, the tread is on the 
whole foot, plantigrade ; while in all the more special- 
ized and agile animals, and especially in the swiftest of 
all, such as the horse, the deer, etc., the heel is high in 
the air, and the tread is digitigrade. 

3. Observe, again: there are two degrees of digiti- 
gradeness. The one we find in carnivorous or clawed 
digitigrades, the other in herbivores or hoofed digiti- 
grades. In the one the tread is on the whole length of 
the toes to the balls, as in man when he ?¢ip-toes ; in 
the other the tread is on the tip of the last joint alone. 
All that in any animal corresponds to the foot of a 
man—i. e., from the hamstring and heel downward— 
is called, in comparative anatomy, the ‘‘ pes.” The pes, 
or foot of a horse, is eighteen inches long, It is easy 
to see what spring and activity this mode of treading 
gives to an animal. Think how helpless a horse would 


be if he trod on the whole foot, heel down ! 
10 


124: EVIDENCES OF THE TRUTH OF EVOLUTION. 


4, Observe, again, the number of toes. In the pro- 
cess of specialization there is a tendency for these to 
become fewer and stronger.* The normal number, as 
already seen, is five. All the earliest mammals, and 
many orders of mammals still living, have five; but in 
the most specialized orders, such as the ungulates or 
hoofed animals, they were steadily reduced in number in 
the course of evolution. In the elephant there are still 
five, in the hippopotamus there are four, in the rhinoce- 
ros three, in the goat two, in the horse one. Still more 
the order of the dropping is regular. If an animal 
have but four toes, it is usually the ‘first, or great toe, 
or thumb, that is wanting, or may be rudimentary. 


* This is only one example under a general law which it may be 


well to stop a moment to illustrate. A repetition of similar parts per- 
forming the same function is always an evidence of low organization, 
and as we rise in the scale of organization such parts usually become 
fewer and more efficient. Thus, to give one example, myriapods, as their 
name indicates, have hundreds of locomotive organs—lower crustaceans 
perhaps thirty or forty. As we go up, they are reduced to fourteen (tet- 
radecapods), then to ten (decapods), then in spiders to eight, in insects 
to six, in vertebrates to four, and in man to two. A similar reduction in 
number, but increase in efficiency, is found in toes, when they are used for 
support and locomotion only. In man we find the normal number of five 
(1), because his hands are used for grasping and the functions of the 
fingers are not the same; and (2), because man’s development was almost 
wholly brainward. In other respects his structure is far less specialized 
than most other mammals. He can not compete with carnivores in 
strength and ferocity, nor with herbivores in fleetness. In the struggle 
for life, therefore, there was nothing left for him but increase in intelli- 
gence. Probably four is the smallest number of locomotive organs con- 
sistent with highest efficiency. In retaining but two legs for locomotion, 
man has lost in locomotive efficiency, but by the sacrifice he liberates two 
limbs for higher functions, 








a ld, i 


,* =) =.) eo, 


PROOFS FROM HOMOLOGIES. 125 


If, as in the rhinoceros, there are only three, then No. 
5, or little toe, is also wanting, and the existing toes 
are Nos. 2, 3, and 4. If an animal has only two toes, 
as the goat, these are Nos. 3 and 4; and if only one, 
as the horse, it is the third or middle toe. Or, to put 
it more definitely : hoofed animals are divided into two 
groups, even-toed (artiodactyl) and odd-toed (perisso- 
dactyl). ‘The even-toed may have four, as in the hip- 
popotamus ; or two, as in the goat. The odd-toed 
may have three, as in the rhinoceros; or but one, as 
in the horse. Now, both of these orders came by dif- 
ferentiation, far back in the Eocene Tertiary, from a 
five-toed plantigrade ancestor. After dropping No. 1 
(thumb or great toe) it is not yet decided, so far as num- 
ber of toes is concerned, whether the resulting four-toed 
animal shall become artiodactyl or perissodactyl. If the 
former, then the two side-toes (Nos. 2 and 5) become 
shortened up, as in the hog; then rudimentary, as in the 
ox and deer; and finally pass away entirely, as in the 
goat. If, on the other hand, the four-toed animal is on 
the line of perissodactyl evolution, it becomes first a 
three-toed animal by dropping No. 5. Now, the two side- 
toes (Nos. 2 and 4) shorten up more and more, and the 
middle toe increases in size, until finally, in the modern 
horse, only the greatly enlarged middle toe (No. 8) re- 
mains. We look with wonder and admiration at the 
danseuse pirouetting on the point of one toe. The 
horse is performing this feat all the time. Yes, the 
one toe of a horse has all the three joimts like ours, 


126 EVIDENCES OF THE TRUTH OF EVOLUTION. 


The coffin-bone is the last joint, and the hoof is the 
nail. 

Genesis of the Horse.—LEvery step of this process on 
the perissodactyl line may be traced in the history of 
the genesis of the horse. The beautiful form and struct- 
ure of this animal were not made at once, but by a slow 
process of integration of small changes from generation 
to generation, and from epoch to epoch of the earth’s 
history. ‘The horse (as in fact did all ungulates) came 
from a five-toed plantigrade ancestor, but we are not 
able to trace the direct line of genesis quite so far. The 
earliest stage that we can trace with certainty, in this 
line of descent, is found in the eohippus of Marsh. This 
was a small animal, no bigger than a fox, with three toes 
behind and four serviceable toes in front, with an ad- 
ditional fifth palm-bone (splint), and perhaps a rudi- 
mentary. fifth toe like a dew-claw. This was in early 
Eocene times. ‘Then, in later Eocene, came the orohip- 
pus, which differs from the last chiefly in the disappear- 
ance of the rudimentary fifth toe and splint. (See Fig. 
25.) Next, in the Miocene, came the mesohippus and 
miohippus. These were larger animals (about the size of 
a sheep), and had three serviceable toes all around; but 
in the former the rudiment of a fourth splint in the fore- 
limb yet remained. Then, in the Miocene, came the pro- 
tohippus and pliohippus. These were still larger ani- 
mals, being about the size of an ass. In the former the two 


side-toes were shortening up and the middle toe becom- — 


ing larger. In the latter the two side-toes have become 





een ee Se te oe ee ee 





Equus: Qua- 
ternary and 
Recent. 


Pliohippus : 
Pliocene. 






Protohippus : 
Lower Plio- 
cene, 


Miohippus : 
Miocene. 


Mesohippus: 
Lower Mio- 
cene. 


Orohippus : 
Eocene, 


Fie. 25.—Diagram illustrating gradual changes in the horse family. 
Throughout a is fore-foot; 4, hind-foot; ¢, fore-arm; d, shank; e, 


molar on side-view; f and g, grinding surface of upper and lower 
molars (after Marsh). 


498. EVIDENCES OF THE TRUTH OF EVOLUTION, 


splints. Lastly, only in the Quaternary comes the genus 
Equus, or true horse. The size of the animal is become 
greater, the middle toe stronger, the side-splints smaller ; 
but in the side-splints of the modern horse we have still 
remaining the evidence of its three-toed ancestor. 

Similar gradual changes may be traced in the two 
leg-bones, which have gradually consolidated into one; 
in the teeth, which have become progressively longer and 
more complex in structure, and therefore a better grind- 
er; in the position of the heel and wrist, which have 
become higher above-ground ; in the general form, which 
has become more graceful and agile; and, lastly, in the 
brain, which has become progressively larger and more 
complex in its convolutions—to give greater battery- 
power, to make a more powerful dynamo—to work the 
improved skeletal machine. See, then, how long it has 
taken Nature to produce that beautiful finished article 
we call the horse! 


We have taken only limbs as examples of what is true 
of the whole skeleton. To the superficial observer the 
bodies of animals of different classes seem to differ fun- 
damentally in plan—to be entirely different machines, 
made each for its own purposes, at once, out of hand. 
Extensive comparison, on the contrary, shows them to 
be the same, although the essential identity is obscured 
by adaptive modifications. The simplest, in fact the 
only scientific, explanation of the phenomena of yverte- 
brate structure is the idea of a primal vertebrate, modi- 








PROOFS FROM HOMOLOGIES. 129 


fied more and more through successive generations by 
the necessities of different modes of life. 

See, then, in conclusion, the difference between man’s 
mode of working and Nature’s. A man having made a 
steam-engine, and desiring to use it for a different pur- 
pose from that for which it was first designed and used, 
will nearly always be compelled to add new parts not 
contemplated in the original machine. Nature rarely 
makes new parts—never, if she can avoid it—but, on the 
contrary, adapts an old part to the new function. It is 
as if Nature were not free to use any and every device to 
accomplish her end, but were conditioned by her own 
plans of structure ; as, indeed, she must be according to 
the derivation theory. For example: In early Devonian 
times fishes were the only representatives of the verte- 
brate type of structure. The vertebrate machine was 
then a swimming-machine. In the course of time, when 
all was ready and conditions were favorable, reptiles were 
introduced. Here, then, is a new function—that of lo- 
comotion on land. We want a walking-machine. Shall 
we have a new organ for this new function ? No: the 
old swimming-organ is modified so as to adapt it for 
walking. Time went on, until the middle Jurassic, and 
birds were introduced. Here is a new and wonderful 
function, that of flying in the air. We want a flying- 
machine. We know how man would have done this; for 
we haye the result of his imagination in angels of Chris- 
tian art and griffins of Greek mythology. He would 
have added wings to already existing parts, and this 


1380 EVIDENCES OF THE TRUTH OF EVOLUTION. 


would have necessitated the alteration of the whole plan 
of structure, both skeletal and muscular. Nature only 
modifies the fore-limbs for this new purpose. If we 
must have wings, we must sacrifice fore-legs. We can 
not have both without violating the laws of morphology. 
Finally, ages again passed, and, when time was fully ripe, 
man was introduced. Now we want some part to per- 
form a new and still more wonderful function. We want 
a hand, the willing and efficient servant of a rational 
mind. We know, again, how man would have done this, 
for we have the result in the centaurs of Greek mytholo- 
gy, in which man’s chest, and arms, and head are added 
to the body of a quadruped. But natural laws must not 
be violated, even for man. If we want hands, we must 
sacrifice feet. Again, therefore, the fore-limbs are modi- 
fied for this new and exquisite function. ‘Thus, in the 
fin of a fish, the fore-paw of a reptile or a mammal, the 
wing of a bird, and the arm and hand of a man, we have 
the same part, variously modified for many purposes. 
Many other illustrations might be taken from the 
skeleton and from other systems, especially the muscular 
and nervous. But in the muscular system the modifica- 
tions have been so extreme that homology is much more 
difficult to trace, and therefore requires more extensive 
knowledge than we yet possess, and more extended com- 
parison than has yet been attempted. It has been traced 
with some success through mammals, and probably will 
be through air-breathing vertebrates—i. e., also through 
birds, reptiles, and amphibians ; but to trace it through 





— pe ee oo Se Oe es 





PROOFS FROM HOMOLOGIES. 131 


fishes seems almost hopeless. In the case of the nervous 
system, and especially of the brain, it is again distinct ; 
but this had better be taken up under another head, 
viz., proofs from ontogeny, Chapter VI. 

In the visceral organs homology is very plain, in fact 
too plain. There is not modification enough in most 
cases even to obscure it, because function is the same in 
all animals. These organs do not, therefore, furnish 
good illustrations of that essential identity in the midst 
of adaptive modification which constitutes the argument 
for the derivative origin of structure. It is the organs 
of animal life that show this most perfectly, because it 
is these that take hold on the environment and are 
modified by it. There are, however, a few striking illus- 
trations to be found among the visceral organs, especially 
the blood-system. This, however, had better also be 
deferred to the chapter on ontogeny. 


CHAPTER VI. 
HOMOLOGIES OF THE ARTICULATE SKELETON. 


We have taken the vertebrate skeleton first, only be- 
cause this department is most familiar. But in reality, 
the most beautiful illustrations of essential identity of 
structure in the midst of infinite diversity of adaptive 
modification for different functions and habits of life, 
and therefore of common origin from a primal form, are 
found in the department of articulates. I use the old 
Cuvierian department articulata, rather than the more 
modern arthropods, because the former includes worms 
also. Now, whether worms should be thus included with 
arthropods, or deserve a whole department to themselvesit | 
matters not for our purposes. It is generally admitted 
that arthropods probably descended from marine worms. 
They all have the same general plan of skeletal structure. 
It will suit my purpose, therefore, to regard worms as 
the lowest form of jointed animals. 

Here, then, we have an entirely different plan of 
structure—a different style of architecture and different — 
mechanical principles of machinery. Instead of a skele- 
ton within and muscles acting on the outside, we have 





HOMOLOGIES OF THE ARTICULATE SKELETON. 133 


the skeleton on the outside, and muscles acting from 
within. Instead of two cavities, a neural and visceral, 
the skeleton forms but one cavity, in which all organs 
are inclosed and protected. Instead of finding the 
nerve-axis on the dorsal aspect of the body, we find it on 
the ventral aspect. 

Take any articulate animal, for example, a shrimp, a 
centiped, or a beetle. Cut it across the body, and look 
at the end (Fig. 26). Weseea ring of bone (chitin) in- 





Fig. 26.—Diagram section across an arthropod, showing the inclosing 
skeleton-ring and a pair of jointed appendages. m, nervous center ; 
v, viscera; 6, blood system. 


closing all the organs (nervous system 7, blood system 8, 
and visceral system v), and a pair of jointed appendages, 
perhaps legs, on each side. Now imagine these parts 
repeated in a linear series. ‘The rings repeated make a 
hollow, jointed tube or barrel, the appendages repeated 
make a continuous row of appendages on each side. Now 


134 EVIDENCES OF THE TRUTH OF EVOLUTION. 


this is exactly what we actually find. The whole articu- 
late skeleton is ideally made up of a series of such re- 
peated rings and appendages, modified according to the 
position in the series, and the uses to which they are 
put. And then the whole articulate department is made 
up of such articulate animals again modified according to 
place in the scale of articulates. The modification in 
the lower forms is slight, and therefore the identity of 
the repeated parts is obvious ; but as we go up the scale, 
and the number and complexity of the functions in- 
crease, the adaptive modification becomes greater and 
greater, until finally it so obscures the essential identity, 
that it requires the most extensive comparison in the 
taxonomic series and in the ontogenic series, to pick up 
the intermediate links and establish the fact of common 
origin. In a word, whether they so originated or not, it 
is certain that the structure of articulate animals is ex- 
actly such as would be the case if all these animals were 
genetically connected, and came originally from a primal 
form something like one of the lower crustaceans, or, 
perhaps, a marine worm, 

It will be best to take an example from about the 
’ middle of the scale, where the two elements, viz., essen- 
tial identity and adaptive modification, are somewhat 
evenly balanced, and both traceable with ease and cer- 
tainty, Take, then, a oray-fish, a lobster, or a shrimp. 
This animal (Fig. 27) has twenty or twenty-one rings 
and pairs of jointed appendages. The rings are some 
of them diminished, some of them increased in size. 











HOMOLOGIES OF THE ARTICULATE SKELETON. 135 


Sometimes several are consolidated ; sometimes several 
are partially or wholly aborted. The appendages are 
modified in shape and 
size, according to their 
position, so as to make 
them swimming-appen- 
dages (swimmerets), 





walking - appendages | 
eee Paving append Fic. ee are vulgaris). 
ages (jaws), and sense- 

appendages (antenne). For example, in the abdomi- 
nal region, or so-called tail, we have seven segments, 
all being perfect movable rings, each with its pair of 
jointed appendages, except the last, or ¢elson. The 
appendages of the first ring (Fig. 28, B) are specially 
modified in the male as organs of copulation (B’). The 
next four pairs are modified for swimmerets (D’) and 
for use as holders of the eggs in the female. The ap- 
pendages of the sixth ring (G) are broad and paddle- 
shaped, and, together with the telson or seventh ring 
(1), form the powerful terminal swimmer. Going, 
now, to the cephalo-thorax : in this either a large num- 
ber of segments (thirteen or fourteen) are consolidated 
above to form the upper shell or carapace; or else, as 
is more probable, two or three of the anterior seg- 
ments have enlarged and grown backward over, and at 
the expense of the others, to form this shell. At any 
rate, it is certain that the carapace is formed of the 
dorsal portions of a number of segments consolidated 





Fig. 28.—External anatomy of the lobster (after Kingsley). 


HOMOLOGIES OF THE ARTICULATE SKELETON. 137 


together. Below, 
however, the seg- 
ments are all dis- 
tinct, and have 
each its own pair 
of appendages. 
For example, go- 
ing forward in 
this region, the 
five next pairs of 
appendages are 
greatly enlarged 
and very strong, 
and serve the pur- _ 
pose of locomo- 





tion. They are 
walking - append- 
ages. The next 


Fig. 30.—Appendages of Nebalia. 


two or three pairs 
are smaller and 
somewhat modi- 
fied, but not so 
much as to ob- 


Fig. 29.—Appendages of a prawn (after Cuvier). 





scure their essen- 
tial similarity to 
legs. Like legs, 
they are many- 
jointed, and like 





legs, too, they 


138, EVIDENCES OF THE TRUTH OF EVOLUTION. 


have gills attached to them. They are called maxilli- 
peds, or jaw-feet. They are used like hands to gather 
food and carry it to the mouth. They are gathering- 
appendages. Then follow three or four pairs still more 
modified, and used for mastication. They are called 
maxilla and mandibles. They are eating-appendages. 
Then follow two pairs, long, many-jointed, with the 
same kind of curious hinge-joints, which we have in 
the legs, undoubtedly homologous with all the others, 
but used for an entirely different purpose, and special- 
ly modified for that purpose. They are the antenne. 
They are delicate organs of touch and of hearing, for 





Fie, 31.—Vibilia, an amphibod crustacean (after Milne Edwards). 


the ear is situated in the basal joint of the anterior 
pair. Last of all, there is still another pair, jointed and 
movable, on the ends of which are situated the eyes. 
These last three, therefore, are sense-appendages. Some 


HOMOLOGIES OF THE ARTICULATE SKELETON. 139 


writers make this last pair special organs, not homolo- 
gous with appendages. 

For the sake of greater distinctness, we give the 
whole series of these appendages in one of the higher 
forms, viz., the prawn (Palemon, Fig. 29, and in one of 
the lower forms, Nebalia, Fig. 30). 


_ 


> DLUtG TF 
LF 


\4 \ 4 \ ke AE 
\ \ \\ A I 
AENEAN 
oexK Q > —= 


Fig. 32.—Lithobius forcipatus (after Carpenter), 


That these are really homologous parts is further 
shown by the fact that in the case of other crustaceans, 
such as limulus, the same appendages, i. e., the append- 
ages of the same body segments, which in the cases be- 
fore mentioned are used as feet, become swimmers, while 
the appendages corresponding to jaw-feet become walk- 
ers; and even what corresponds to antenne or sense- 
appendages, may, as in branchippus, become powerful 
claspers. Finally, in all the lowest crustaceans, the 
identity is evident, because all the segments and their 
appendages are much alike in form and function (Fig. 
31). 

We have taken examples from near the middle of the 
articulate scale, because, as already stated, both the essen- 
tial identity and the adaptive modifications are easily 

oe 


140 EVIDENCES OF THE TRUTH OF EVOLUTION, 


traced. If we go downward in the scale, the structure 
becomes more and more generalized, and the rings and 
appendages become more and more alike (Fig. 31), until 
in the most generalized forms we have only a series of 
similar rings, with similar pairs of appendages, except 
some necessary modifications to form the head and tail. 
This is well shown in the centiped (Fig. 32), and still 
better in marine worms (Fig. 33). In some marine 
worms the slight modification to form the head takes 





Fie. 33.—Syllis prolifera. 


place under our very eyes. These often multiply by di- 
viding themselves into two. When they do so, they make 
a new head and new tail by slight modification of seg- 
ments and appendages (Fig. 33). 

If, on the other hand, we go up the scale, we find 
adaptive modifications obscuring more and more the 
simple and obvious identity of parts, until finally the — 
identity can not be recognized without extensive com- 
parison in the taxonomic series and study of embryonic 
conditions. In crabs—which is a higher form than cray- 
fish—the tail or abdomen seems to be wanting, but is only 
very small and bent under the body and thus concealed. 
In all essential respects the structure is precisely like the 


HOMOLOGIES OF THE ARTICULATE SKELETON. 141 


cray-fish. In fact, in the embryo, we trace the one form 
into the other; for the crab is at first a long-tailed crus- 
tacean (Fig. 34). 

Insects are the highest form of articulates. In these, 
therefore, we find the modification is still greater than in 





Fig, 34.—Development of Carcinus meenas, a, zowa stage; B, megalopa 
stage ; C, final state (after Couch). 

crustaceans, though even here the ring-and-appendage 

structure is plain enough in most cases. 

One of the best evidences of high grade among ani- 
mals is the gathering of the segments into distinct 
groups, and especially the distinctness of the head as one 
of these groups. In worms and lower crustaceans there 
is no grouping at all, the skeleton being a continuous 
series of joints, only slightly modified at the anterior 
and posterior extremities. In the higher crustacea, and 
in spiders and scorpions, they are grouped into two 


149. EVIDENCES OF THE TRUTH OF EVOLUTION. 


cate, Vd 
Labruwm 
a <e C\itandible f 


| Tarsus\, Polp RSQ 
ay x © JX 
Labi 





/ Epreranit 


YWresothorax 


Scutellum 


athoray 


=> ey, 
Fie. 85.—External anatomy of Caloptenus spretus, the head and thorax 
disjointed ; up, uropatagium ; 7, furcula; ¢, cercus (drawn by J. T. 
Kingsley). 


HOMOLOGIES OF THE ARTICULATE SKELETON. 143 


regions, Viz., cephalo-thorax and abdomen. In insects 
they are grouped into three very distinct regions—head, 
thorax, and abdomen. In insects, therefore, we find for 
the first time the head distinctly separated from the rest 
of the body. This is an evidence of high grade, because 
it shows the dominance of head-functions. 

The insect, such, for example, as a grasshopper, con- 
sists of seventeen or eighteen segments (Fig. 35). Of 
these, four belong to the head, three to the thorax, and 
about ten to the abdomen. ‘Those of the abdomen are 
all separated and movable ; those of the thorax and head 
are more or less consolidated. The appendages of the 
head-segments become antenne and jaw-parts, 1. e., mandi- 
bles—maxille and labium ; the appendages of the thorac- 
segments become legs (the wings are not homologous 
with appendages), while those of the abdomen are aborted. 
The steps of the gradual consolidation on the one hand, 
and the abortion on the other, may be traced in the em- 
bryo or larva—i. e., in the caterpillar or the grub of a 
bee or a beetle. In the caterpillar, for example, there is 
no grouping into three regions, there is no consolida- 
tion, and all the segments have appendages. Again, the 
almost infinite variety in the mouth-parts among in- 
sects, brought about by adaptive modifications for biting, 
for piercing, and for sucking, and yet the essential iden- 
tity of all to the more simple and generalized structure 
of the grasshopper, is an admirable illustration of the 
same principle. But to dwell upon these minor points 
would carry us too far. 


144 EVIDENCES OF THE TRUTH OF EVOLUTION. 


Yllustration of the Law of Differentiation.—We have 
here, in the modifications of segments and appendages of 
articulates, an admirable illustration of the most funda- 
mental law of evolution, viz., the law of differentiation. 
As we have already seen (page 21), perhaps the most 
beautiful and certainly the most fundamental illustra- 
tion of this law is found in the development of cell- 
structure. Commencing in the lowest animals, and in 
the earliest embryonic stages of the higher animals, 
from a condition in which all are alike, the cells as we 
go upward quickly diverge into different forms to pro- 
duce different tissues and perform different functions. 
Here, then, we have a perfect example of essential iden- 
tity and adaptive modification. It is the very best type 
of differentiation. So also skeletal segments, commenc- 
ing, in the lowest articulates and in earliest embryonic 
stages of the higher, all alike, as we go upward in either 
series, begin immediately to diverge in various directions 
(divergent variation), taking different forms to subserve 
different uses. Here, again, therefore, is an illustration 
of the law of differentiation. Lastly, in the articulate 
department, commencing with the lowest forms and earli- 
est embryonic conditions, and we may add earliest geo- 
logical times, and going up either series from generalized 
forms very much alike, the individuals are gradually 
differentiated into many special forms, in order to adapt 
them to the diversified modes of hfe actually found in 
nature. Thus cells, segments, individuals, are all alike 
affected by this most fundamental law. 


HOMOLOGIES OF THE ARTICULATE SKELETON. 145 


We have taken our illustrations from only the two de- 
partments of vertebrata and articulata, because these are 
the most familiar to the reader, and also have been most 
carefully studied. We have shown that the general 
structure of all vertebrates is precisely what it would be if 
they all had come from one primal vertebrate form, and 
that of all articulates what it would be if all had come 
from one primal articulate form. The only natural ex- 
planation, and, therefore, the only scientific explanation 
of this, is that they were really thus derived. 'The same 
kind of evidence may be drawn from the study of other 
departments, but to pursue the subject any further in 
this direction would carry us beyond the limits which 
we have assigned. We desire only to explain the nature, 
not to give all, of the evidence. The examples given will 
be sufficient for the purposes of illustration. The whole 
proof is nothing less than the whole science of compara- 
tive anatomy. 

Vertebrates, then, were derived from a primal verte- 
brate, articulates from a primal articulate, and so for other 
departments. But whence were these primals derived ? 
Are there any intermediate links between, any deeply 
concealed common plan of structure underlying these 
primary groups, showing a common origin ? It must be 
confessed that, in their mature condition, there seems to 
be but little evidence of such. ‘These primary groups 
seem to be built on different plans, to be fundamentally 
of different styles of architecture. Therefore Darwin, in 
the true spirit of inductive caution—that true scientific 


446 EVIDENCES OF THE TRUTH OF EVOLUTION. 


spirit which keeps strictly within the limits of evidence 
—commences with four or five distinct primal kinds, 
from which by divergent variation all animals were de- 
scended. Nevertheless, the truly scientific biologist 
must ever strongly incline to believe that these also 
came from some primal animal, and even that both 
animals and plants were derived from some primal form 
of living thing; that as, in the taxonomic series, the 
animal and vegetal kingdoms in their lowest forms 
merge undistinguishably into one another; as in the 
ontogenic series the animal and plant germ are one, 
so also in the phylogenic series the earliest organisms 
were simply living things, but not distinctively ani- 
mal nor vegetal. Science, therefore, whose mission is to 
trace origins as far back as possible, must ever strive to 
find connecting links between the primary groups. Some 
such have been supposed to have been discovered. Some 
find the origin of vertebrates among the molluscoids (as- 
cidians); some find the origins of both vertebrates and 
articulates among marine worms (annelids). This point 
is still too doubtful to be dwelt upon here. It may be 
that we seek in vain for such connecting links among 
existing forms. It may well be that the point of separa- 
tion of these great primary groups (unless we except 
vertebrates) was far lower even than these low forms. 
Both phylogeny and ontogeny seem to indicate this. In 
the earliest fauna known, the primordial (for if there was 
life in the archean it was not yet differentiated into a 
fauna), all the great departments, except the vertebrates, 


HOMOLOGIES OF THE ARTICULATE SKELETON. 147 


seem to have been represented. In embryonic develop- 
ment, too, the point of connection or even of similarity, 
between the great departments, is found, as we shall see 
hereafter, only in the earliest stages—i. e., lower down 
than any but the lowest existing forms, viz., the pro- 
tozoa, 


CHAPTER VII. 


PROOFS FROM EMBRYOLOGY, OR COMPARISON IN THE 
ONTOGENIC SERIES. 


It is a curious and most significant fact that the suc- 
_ cessive stages of the development of the individual in the 
higher forms of any group (ontogenic series) resemble 
the stages of increasing complexity of differentiated 
structure in ascending the animal scale in that group 
(taxonomic series), and especially the forms and structure 
of animals of that group in successive geological epochs 
(phylogenic series). In other words, the individual 
higher animal in embryonic development passes through 
temporary stages, which are similar in many respects to 
permanent or mature conditions in some of the lower 
forms in the same group. To give one example for the 
sake of clearness: The frog, in its early stages of embry- 
onic development, is essentially a fish, and if it stopped 
at this stage would be so called and classed. But it does 
not stop ; for this is a temporary stage, not a permanent 
condition. It passes through the fish stage and through 
several other temporary stages, which we shall explain 
hereafter, and onward to the highest condition attained 


PROOFS FROM EMBRYOLOGY. “3; “149 


by amphibians. Now, if we could trace perfectly the 
successive forms of amphibians, back through the geo- 
logical epochs to their origin in the Carboniferous, the 
resemblance of this series to the stages of the develop- 
ment of a frog would doubtless be still closer. Surely 
this fact, if it be a fact, is wholly inexplicable except by 
the theory of derivation or evolution. The embryo of a 
higher animal of any group passes mow through stages 
represented by lower forms, because in its evolution (phy- 
logeny) its ancestors did actually have these forms. From 
this point of view the ontogenic series (individual his- 
tory) is a brief recapitulation, as it were, from memory, 
of the main points of the philogenic series, or family his- 
tory. We say brief recapitulation of the main points, 
because many minor points are dropped out. Hvyen some 
main points of the earliest stages of the family history 
may be dropped out of this sort of inherited memory. 
This resemblance between the three series must not, 
however, be exaggerated. Not only are many steps of 
| phylogeny, especially in its early stages, dropped out in 
the ontogeny, but, of course, many adaptive modifica- 
tions for the peculiar conditions of embryonic life are 
added. But it is remarkable how even these—for exam- 
ple the umbilical cord and placenta of the mammalian > 
‘embryo—are often only modifications of egg-organs of 
lower animals, and not wholly new additions. It is the 
similarity in spite of adaptive modifications that shows 
the family history. 
We will now illustrate by a few striking examples. 


150: EVIDENCES OF THE TRUTH OF EVOLUTION. 


We can not do better than to take, again, as our first 
example, the development of tailless amphibians, and 
dwell a little more upon it : 

1. Ontogeny of Tailless Amphibians.—It is well 
known that the embryo or larva of a frog or toad, when 
first hatched, is a legless, tail-swimming, water-breathing, 
gill-breathing animal. It is essentially a fish, and would 
be so classed if it remained in this condition. The fish 
retains permanently this form, but the frog passes on. 
Next, it forms first one pair and then another pair of 
legs; and meanwhile it begins to breathe also by lungs. 
At this stage it breathes equally by lungs and by gills, 
1.e., both air and water. Now, the lower forms of am- 
phibians, such as siredon, menobranchus, siren, etc., re- 
tain permanently this form, and are therefore called 
perennibranchs, but the frog still passes on. ‘Then the 
gills gradually dry up as the lungs develop, and they now 
breathe wholly by lungs, but still retain the tail. Now 
this is the permanent, mature condition of many amphi- 
bians, such as the triton, the salamander, etc., which are 
therefore called caductbranchs, but the frog still passes on. 
Finally, it loses the tail, or rather its tail is absorbed and 
its material used in further development, and it becomes 
a perfect frog, the highest order (anowra) of this class. 

Thus, then, in ontogeny the fish goes no further than 
the fish stages. The perennibranch passes through the 
fish stage to the perennibranch amphibian. The caduci- 
branch takes first the fish-form, then the perennibranch- 
form, and finally the caducibranch-form, but goes no 


PROOFS FROM EMBRYOLOGY. 151 


further. Last, the anoura takes first the fish-form, then 
that of the perennibranch, then that of the caduci- 
branch, and finally becomes anoura. This is shown in 
the diagram, which must be read upward, line by line. 


FISH, PERENNIBRANCH. CADUCIBRANCH, ANOURA, 
FISH. PERENNIBRANCH, CADUCIBRANCH. 
FISH, PERENNIBRANCH. 
7? 
FISH, 
Diagram showing the stages of development of amphibians. (To be read 
upward.) 


Now, this is undoubtedly the order of succession of 
forms in geological times—i. e., in the phylogenic series. 
This series is indicated by the arrows in the diagram. 
Fishes first appeared in the Devonian and Upper Silurian 
in very reptilian or rather amphibian forms. Then in 
the Carboniferous, fishes still continuing, there appeared 
the lowest—i. e., most fish-like—forms of amphibians. 
These were undoubtedly perenmbranchs. In the Per- 
mian and Triassic higher forms appeared, which were cer- 
tainly caducibranch. Finally, only in the Tertiary, so far 
as we yet know, do the highest form (anoura) appear. 
The general similarity of the three series is complete. 
If we read the diagram horizontally, we have the onto- 
genic series ; 1f diagonally with the arrows, we have both 
the taxonomic and the phylogenic series. 

2. Aortic Arches.—But some will, perhaps, say that 
these stages in the ontogeny are only examples of adapt- 


152 EVIDENCES OF THE TRUTH OF EVOLUTION, 


ive modifications—like modifications for like conditions 
of life—and had better be accounted for in this way, 
without reference to family history. We will, therefore, 


take another example, which can not be thus accounted 


for—an example in which there is no possible use now 


for the peculiar form or structure which we find. For 








1! ) ae ; 


Fic. 36.—Showing heart and out- 
going blood-vessels of a lizard 
(after Owen). The arrows 
show the course of the blood. 


this purpose we take the 
case of the course of circu- 
lation in vertebrates. 

If one examines the large 
vessels going out from the 
heart of a lizard, he will find 
six aortic arches—i. e., 
three on each side. These 
all unite below to form the 
one descending abdominal 
This is shown in the 
accompanying figure (Fig. 
36), in which a a’ a” and 
b b'b" are the six arches. 
Now, there is no conceiva- 


aorta. 


ble use in having so many 
We know 
this, because there is but 


aortic arches. 


one in birds and mammals, 
and the circulation is as 


effective, nay, much more effective in these than in 
reptiles. The explanation of this anomaly is revealed 
at once as soon as we examine the circulation of a fish, 


PROOFS FROM EMBRYOLOGY. ot Lo 


which is shown in the accompanying figure (Fig. 37). 
The multiplication of the aortic arches is here, of 
B 


Lp 


iis 
) =} 
= y 
Sy y) 
"0 
1} 


} 


it ft 


\ 


CM 


aiaaas wmnoe 
l I\ \ i 








Fig. 87.—<, heart and gill-arches of a fish; B, one arch with fringe 
(after Owen); H, the heart. 
course, necessary, for they are the gill-arches. The 
whole of the blood passes through these arches, to be 
aérated in the gill-fringes. The use of this peculiar 
structure is here obvious enough. If a lizard were ever 
a fish, and afterward turned into a lizard, changing its 
gill-respiration for lung-respiration, then, of course, the 
useless gill-arches would remain to tell the story. Now, 
although a lizard never was a fish, in its individual his- 
tory or ontogeny, it was a fish in its family history or 
phylogeny, and therefore it yet retains, by heredity, this 
curious and wseless structure as evidence of its ancestry. 
That this is the true explanation is demonstrated by 
the fact that in amphibians this very change actually 


154 EVIDENCES OF THE TRUTH OF EVOLUTION. 


takes place before our eyes in the individual history. We 
have already seen that the individual frog, in its tadpole 
state, isa gill-breather. It has therefore its gill-arches 





‘N 


- 


Fia. 39. 


Fics. 38, 39.—Diagrams showing the change of the course of blood in 
the development of a frog. 388. The tadpole stage. 89. The mature 


gen. Fs 


condition. u, heart; @@’@”, external gills; g 79 , internal gills; 
m 


ec, connecting branches in the tadpole; pp, pulmonary branches. 


PROOFS FROM EMBRYOLOGY. 155 


(Fig. 38), three on each side, like a fish, and for the same 
reason, viz., the aération of the blood. But when its gills 
dry up and lung-respiration is established, its now useless 
gill-arches still remain as aortic arches, to attest their 
previous condition (Fig. 39). Now, the lizard undoubt- 
edly came from an air-breathing, tailed amphibian, and 
therefore inherited this form of arterial distribution. In 
both lizard and amphibian the ultimate cause is an origin 
from fishes, in which such arches are obviously necessary. 
The diagrams, Figs. 88 and 39, are illustrations some- 
what idealized, showing the manner in which the change 
actually takes place in air-breathing amphibians. Fig. 
388 represents the tadpole stage, and Fig. 39 the mature 
condition. In the former the gills are mostly external, 
GG’, etc., but also internal, gg’, as in the fish. Observe 
in this condition the small connecting vessels, ec’. When 
the external gills dry up, these are enlarged, and the 
whole of the blood passes through them, as shown in 
Fig. 39. It is seen, also, in Fig. 38, that a small branch, 
p, goes from the lower gill-arches to the yet rudimentary 
lung, 7. When the gill-fringes have disappeared, the 
whole of the blood of the lower arch goes through the 
now enlarged pulmonary branch to the lungs, L, now in 
full activity, and the remainder of this arch disappears, 
as shown by the dotted lines in Fig. 39. 

The change which actually took place in the family 
history of the lizard probably differed from the above 
only in being more simple, the gills being only internal 
like the fish. The external gills complicate the process 

12 


15@ EVIDENCES OF THE TRUTH OF EVOLUTION. 


a little in the case of the frog, but the principle is pre- 
cisely the same. 

' As already explained (pages 82-85), the large gap be- 
tween fishes and reptiles, as regards mode of respira- 
tion, is completely filled both in the taxonomic series 
—i. e., in ganoids, dipnoi, and the mature condition of 
the different orders of amphibians—and in the ontogeny 
of the higher amphibians. Now, we add that the same 
is true of the arterial distribution. We have just traced 
the change in the ontogeny of the frog, but the steps of 
the same change are traceable in passing from the typical 
fish (teleosts), through dipnoi and amphibians to rep- 
tiles. Thus, again, the phylogeny, the taxonomy, and 
the ontogeny, are in complete accord. 

But the argument for evolution does not stop here. 
If birds and mammals have come from reptiles, and 
therefore from fishes, we may expect to find some evi- 
dences of the same kind still lingering in the great arter- 
ies. And such we do find. It is a most curious and 
significant fact that, in the early embryonic condition of 
birds and mammals, including man himself, we find 
on each side of the neck several gill-slits, each with its 
gill-arch, and therefore several aortic arches on eath 
side, precisely similar to what we have already described. 
These arches are subsequently, some of them, obliterated ; 
some modified to form the one aortic arch, and some 
of them still more modified to form the other great arter- 
ies coming from the heart to supply the head and fore- 
limbs. 


PROOFS FROM EMBRYOLOGY. _ 157 


This is so beautiful and convincing an example, and 
one so generally unfamiliar, to even intelligent persons, 





Fig, 40.—Diagram of mammalian heart. a, aorta; p, pulmonary artery ; 
ses'c’, subclavium on each side; cc’, carotids on each side. 
not especially acquainted with biology, that it is best to 
explain it more fully. In Fig. 40 we give a mammalian 
heart and outgoing vessels, very slightly modified, so as 
to suggest the process of change. In Fig. 41 we give 
an ideal diagram representing the primitive aortic arches 
as they exist in the embryo of mammals, birds, and 
reptiles. It represents, also, substantially, the arches as 
they exist in the mature condition in the most reptilian 
fishes (dipnoi) and in some sharks, except that in these — 


158 EVIDENCES OF THE TRUTH OF EVOLUTION. 


the arches are of course furnished with gill-fringes. We 
will use this figure, therefore, to represent both the em- 





Fig. 41.—Ideal diagram representing Fig. 42.—Modified for bird. 
the primitive aortic arches (after 
Rathke). 


bryonic condition of air-breathing vertebrates and the 
mature condition of some fishes. The place of the heart 
is indicated by the dotted circle. Fig. 36, on page 134, 
shows what these arches become in reptiles (lizard). It is 
seen that the two upper arches on each side are obliterated, 
as indeed they already are in some teleost fishes. Fig. 42 
shows what they become in birds. The two upper arches 
are, of course, obliterated. The others are all modified, 
each in a manner which may be readily understood by 


PROOFS FROM EMBRYOLOGY. 159 


comparison with Fig. 41. Finally, Fig. 43 shows what they 
become in mammals and in man. In the bird (ig. 42) 
the first pair of arches become the two pulmonary arteries 
as they do also in the lizard. The second pair become on 
the right side (left of 
the diagram) the aortic 
arch, on the left side 
(right of the diagram) 
the left subclavian, s’c’ 
(the right subclavian, 
sc, 1s a branch of the 
aortic arch). The third 
pair become carotids, 
cc, while the fourth and 
fifth, as already said, are 
aborted. In the mam- 
mal (Fig. 43), on the left 
side (right of the dia- 
gram) the first arch be- 





Fia, 43.—Modified for mammal. 


comes the pulmonary 
artery, p. In the foetus the continuation of this arch 
forms the ductus arteriosus, which is afterward obliter- 
ated, as shown in the dotted line. The second arch be- 
comes the aortic arch, the third the left exterior carotid. 
On the right side (left of the diagram) the first arch 
becomes aborted; the second, the right subclavian, sc 
(the Zef¢ subclavian, s’c’, is a branch of the aortic arch) ; 
and the third, the right carotid. Nos. 4 and 5, on both 
sides, as usual, are aborted. 
































cry 


Lie 






LL 






=< 


<== 
———— 
ee ~ << SOOO 
mee sae ae 






160 EVIDENCES OF THE TRUTH OF EVOLUTION. 


See, then, the gradual process of 
change through the whole vertebrate 
department. In the lowest of all ver- 
tebrates, if vertebrate it may be called 
(for what corresponds to its backbone 
is an unjointed, fibrous cord), the am- 
phioxus or lancelet (Fig. 44), there are 
about forty gill-arches on each side. 
As we rise in the scale of fishes these 
are reduced in number. In the lam- 
prey, there are seven ; in the sharks, 
usually five; in ordinary fishes (tele- 
osts), there are four or sometimes only 
three on each side, the others being 
aborted. Thus far the change is only 
by diminution of number in accordance 
with a law universal in biology, that 
decrease in the number of identical 
organs is evidence of. advance in the 
grade of organization, provided that it 
be associated with more perfect struct- 
ure of the organ. The further change 
is one of adaptive modification. In 
some reptiles (lizard) the three gill- 
arches on each side all retain the form 
of aortic arches; in some reptiles only 


Fie. 44. — Lancelet two retain this form. In birds and 
(Amphioxus lan- ; : ; 
ceolatus). Mag- mammals only one arch is retained, in 


nified two and ° 
one-half times, | the form of aortic arch, the others be- 


PROOFS FROM EMBRYOLOGY. 161 


ing modified to form the great outgoing vessels of the 
heart, or else aborted. It may be well to observe that in 
birds the one aortic arch turns to the right, while in 
mammals it turns to the left. This is positive evidence 
that mammals could not have come from birds, nor vice 
versa. They both came from reptiles, and, of the many 
reptilian arches, a right one was retained by the bird 
branch, and a left one by the mammalian. 

In all the figures illustrating this subject, we have left 
out the great incoming vessels or veins, because we are 
not here concerned with them, they not being trans- 
formed gill-arches. 

Last of all, it may be well to stop a moment to show 
the cogency of this evidence. If it were a question of 
the origin of some structure not only useful (for all struct- 
ures selected by Nature must be useful) but the Jest 
imaginable, like the eye or the ear, for example ; then, if 
we examined only the highest form or the finished article, 
there are two ways in which it is possible to explain the 
adaptive structure. We may either suppose that it was 
made at once out of hand, by some intelligent contriver ; 
or else that it was slowly made by a process of evolution, 
becoming more and more perfect by a selection of only 
the most perfect from generation to generation. But in 
the case of the six aortic arches of the lizard, we are shut 
up to the one explanation only, viz., by slow process of 
evolution. One arch is all that is necessary, as is plainly 
shown by the use of only one in the more perfect circula- 
tion of birds and mammals. If the thing were done out 


162 EVIDENCES OF THE TRUTH OF EVOLUTION. 


of hand, unconditioned by the previous structure in 
fishes, to have made six was surely but a bungling piece 
of work. ; 

3. Vertebrate Brain.—Another excellent example is 
the structure of the vertebrate brain. ‘The brain of an 
average fish is represented in Fig. 45. It consists of four 





Fie. 45.—Fish-brain. a, side view ; B, top view. 


or five swellings, or ganglia, strung along, one beyond 
another. Commencing-behind, these are, first, the me- 
dulla, m ; then the cerebellum, cd; then the optic lobes, 
ol ; then the cerebrum and thalamus combined, er ; and 
last, the olfactive lobes, of. Of these, it will be observed, 
the optic lobe is the largest in the brain of the fish (Fig. 
45). In the brain of the reptile (Fig. 46) we have the 





Fic. 46.—Reptile-brain. a, side view ; B, top view. 


same serial arrangement, of the same parts, only that the 
cerebrum has now become the dominant part instead of 
the optic lobes. In the average bird (Fig. 47) the cere- 
brum has grown so large that it extends backward, and 
partly covers the optic lobes. In the lower mammals 
(marsupials), the brain is much the same in this respect, 


PROOFS FROM EMBRYOLOGY. 163 


as in birds—i. e., the cerebrum only partly covers the 
optic lobes, so that, looked at from above, the whole se- 





Fig. 47.—Bird-brain, 4, side view ; 3B, top view. 


ries of ganglia are still visible. But in the average mam- 
mal (Fig. 48) the cerebrum is so enlarged that it covers 





Fie. 48.—Mammal-brain. 4, top view; B, side view. 
entirely the optic lobes and encroaches on the cerebellum 
behind and the olfactive lobes in front. In some mon- 
keys, indeed, the cerebellum is nearly or even quite 
covered. Finally, in man (Fig. 49), the cerebrum has 


A B 





Fic. 49.—Man’s brain. A, side view; B, top view. 


164 EVIDENCES OF THE TRUTH OF EVOLUTION. 


grown so enormously that it covers every other part and 
completely conceals them from view when the brain is 


looked at from above. In front it not only covers but 
WWMOM . 





Fra. 50.—Ideal section showing all the above stages. 


has grown far beyond the olfactive lobes ; behind it ex- 

tends beyond and overhangs the cerebellum; on the 

sides it overhangs and 

covers all. Looked at 

from above, nothing is 

m seen but this great 

ganglion. The ideal 

section (Fig. 50) rep- 

Fig, 51.—Sub-fish stage. th, thalamus; resents all these stages 

ol, optic lobe ; m, medulla, : : . 

diagrammatically in 

one figure. After what has been said, the figure will 
be readily understood. 


PROOFS FROM EMBRYOLOGY. 165 


Now, it isa most remarkable fact that substantially 
these same stages, which are permanent conditions in the 


Fig. 52.—Fish-stage. of, olfactive lobe; er, cerebrum; ¢A, thalamus; 
ol, optic lobe; cb, cerebellum; m, medulla. 

taxonomic series, are passed through as transient stages in 

the embryonic development of the human brain, and in 

the order given above. The very early condition of the 

human brain is represented in Fig. 51. It is evidently 





Fic. 53.—Reptile-stage. 


nothing more than the intercranial continuation of the 
spinal cord, enlarged a little into three swellings or gan- 
glia. ‘These are the early representatives of the medul- 
la, the optic lobes, and the thalamus ; which last may 
be regarded as the basal and most fundamental part of 
the cerebrum. This stage may be regarded as lower 
than that of the ordinary fish. I have called it, therefore, 
the sub-fish stage. ‘The cerebellum is a subsequent out- 
growth from the medulla, as is the cerebrum and olfac- 


166 EVIDENCES OF THE TRUTH OF EVOLUTION. 


tive lobes from the thalamus. Fig. 52 may be said, there- 
fore, to represent fairly the fish-stage. Henceforward the 
principal growth is in the cerebrum and cerebellum, 
both of which are subsequent outgrowths of the origi- 
nal simple ganglia, the medulla, and the thalamus. The 
cerebrum especially increases steadily in relative size, first 
becoming larger than but not covering the optic lobes 
(Fig. 53). This represents the reptilian stage. Next, by 


th 
of 


Fie, 54.—Bird-stage. of, olfactive lobe; ev, cerebrum; ¢h, thalamus; 
ol, optic lobe; cb, cerebellum; m, medulla. 


further growth, it covers partly the optic Ipbes (Fig. 
54). This may be called the bird-stage. Then it 





Fig. 55.—Mammalian stage. 


PROOFS FROM EMBRYOLOGY. 167 


covers wholly the optic lobes, and encroaches on the 
cerebellum behind and olfactive lobes in front (Fig. 55). 
This is the mammalian stage. Finally, it covers and 


cr 


ol Lb 


th 


“yy 


of 


Wee 
Mex 


Fig. 56.—Human stage. 


overhangs all, and thus assumes the human stage (Fig. 
56). 

We have spoken thus far only of relative size; but 
progressive changes take place also in complexity of 
structure—i. e., in the depth and number of convolu- 
tions of the cerebrum and cerebellum. The cerebrums 
of fish, of reptile, bird, and lower mammals are smooth. 
About the middle of the mammalian series it begins to 
be convoluted. These convolutions become deeper and 
more numerous as we go upward in the scale, until they 
reach the highest degree in the human brain. 'The ob- 
ject of these inequalities is to increase the surface of gray 
matter—i. e., the extent of the force-generating as com- 


168 EVIDENCES OF THE TRUTH OF EVOLUTION. 


pared with the force-transmitting part of the brain, or 
battery as compared with conducting-wire. Now, in 
embryonic development the human brain passes also 
through these stages of increasing complexity of organi- 
zation. Here also the ontogenic is similar to the taxo- 
nomic series. 

Now, why should this peculiar order be observed in 
the building of the individual brain? We find the an- 
swer, the only conceivable scientific answer to this ques- 
tion, in the fact that this ts the order of the building of 
the vertebrate brain by evolution throughout geological 
history. We have already seen that fishes were the only 
vertebrates living in the Devonian times. . The first form 
of brain, therefore, was that characteristic of that class. 
Then reptiles were introduced; then birds and marsu- 
pials; then true mammals; and, lastly, man. The differ- 
ent styles of brains characteristic of these classes were, 
therefore, successively made by evolution from earlier 
and simpler forms. In phylogeny this order was ob- 
served because these successive forms were necessary for 
perfect adaptation to the environment at each step. In 
taxonomy we find the same order, because, as already ex- 
plained (page 11), every stage of advance in phylogeny 
is still represented in existing forms. In ontogeny we 
have still the same order, because ancestral characteris- 
tics are inherited, and family history recapitulated in 
the individual history. 

But not only is this order found in the evolution 
of the whole vertebrate department, but something of 


PROOFS FROM EMBRYOLOGY. 169 


the same kind is found also in the evolution of each 
class. 'The earliest reptiles, the earliest birds, and the 
earliest mammals had smaller and less perfectly organ- 
ized brains than their nearest congeners of the present 
day. ‘This is shown in the accompanying figures (Figs. 
5% and 58). ‘To carry out one example more perfectly : 
In the history of the 
horse family, in con- 


A B 


nection with the chang- 
es of skeletal structure 
already described (page 
108), we have also cor- 
responding changes in 
the size and structure 
of the brain ; pari pas- 
su with the improve- 
ment of the mechan- 
ism we have also in- 
creased engine - power 
and increased muscu- 
lar energy and there- 
fore increased activity 
and grace. The brain 
of a modern horse, 





though not very large, 


is remarkable for the Fie. 57.—a, brain of extinct Ichthyornis ; 
’ f B, modern tern, 

complexity of its con- 

volutions. The great energy, activity, and nervous ex- 


citability of the horse are the result of this structure. 


170 EVIDENCES OF THE TRUTH OF EVOLUTION. 





7 Se 
§$ Ze 


Fic. 58,—a, brain of Eocene dinoceras ; B, Miocene brontothere ; c, mod- 
ern horse, 


PROOFS FROM EMBRYOLOGY. 1d 


Cephalization—Thus, in going up the phylogenic, 
the taxonomic, or the ontogenic series, we find a gradual 
process of development headward, brainward, cerebrum- 
ward ; or, more generally, we might say that in all or- 
ganic evolution we find an increasing dominance of the 
higher over the lower, and of the highest over all. For 
example, in the lowest plane of either series we find first 
the different systems imperfectly or not at all differen- 
tiated. ‘Then, as differentiation of these progress, we 
find an increased dominance of the highest system—the 
nervous system; then in the nervous system, the in- 
creasing dominance of its highest part—the brain ; 
then in the brain the increasing dominance of its high- 
est ganglion—the cerebrum; and, lastly, in the cere- 
brum the increasing dominance of its highest sub- 
stance—the exterior gray matter—as shown by the in- 
creasing number and depth of the convolutions. This 
whole process may be called cephalization. 

Shall the process stop here? When evolution is 
transferred from the animal to the human plane, from 
the physiological to the psychical, from the involuntary 
and necessary to the voluntary and free, shall not the 
same law hold good? Yes! all social evolution, all 
culture, all education, whether of the race or the indi- 
vidual, must follow the same law. All psychical ad- 
vance 1s a cephalization—i. e., an increasing dominance 
of the higher over the lower and of the highest over 
all; of the mind over the body, and in the mind of 


the higher faculties over the lower; and, finally, the 
13 


179 EVIDENCES OF THE TRUTH OF EVOLUTION, 





Fig. 59.—Homocercal tail-fin, 
A, form; B, structure. 


subordination of the whole to 
the highest moral purpose. 
4, Fish-Tails. — Still an- 
other and last example: lt 
has long been noticed that 
there are among fishes two 
styles of tail-fins. These are 
the even-lobed, or homocercal 
(Fig. 59), and the uneven- 
lobed, or heterocercal (Fig. 
60). The one is character- 
istic of ordinary fishes (tele- 
osts), the other of sharks and 
some other orders. In struct- 
ure the difference is even 


more fundamental than in form. In the former style 
the backbone stops abruptly in a series of short, enlarged 
joints, and thence sends off rays to form the tail-fin 





Fig, 60.—Tleterocercal or vertebrated tail-fin. a, form; B, structure. . 


PROOFS FROM EMBRYOLOGY. 173 


(Fig. 59, B); in the latter the backbone runs through 
the fin to its very point, growing slenderer by degrees, 
and giving off rays above and below from each joint, 
but the rays on the lower side are much longer (Fig. 60, 
B). This style of fin is, therefore, vertedrated, the other 
non-vertebrated. Figs. 59 and 60 show these two styles 
in form and structure. But there is still another style 
found only in the lowest and most generalized forms of 
fishes. In these the tail-fin is vertebrated and yet sym- 
metrical. This style is shown in Fig. 61, A and B. 





Fie. 61.—Vertebrated but symmetrical fin. a, form; B, structure. 


Now, in the development of a teleost fish (Fig. 58), 
as has been shown by Alexander Agassiz,* the tail-fin is 
first like Fig. 61; then becomes heterocercal, like Fig. 60; 
and, finally, becomes homocercal like Fig. 59. Why so? 
Not because there is any special advantage in this succes- 
sion of forms; for the changes take place either in the 
egg or else in very early embryonic states. The an- 
swer is found in the fact that this 7s the order of change 


* “Proceedings of American Academy of Arts and Sciences,” vol, 
xiv, May, 1878. 


174 EVIDENCES OF THE TRUTH OF EVOLUTION. 


in the phylogenic series. The earliest fish-tails were 
either like Fig. 61 or Fig. 60; never like Vig. 59. The 
earliest of all were almost certainly like Fig. 61; then 
they became like Fig. 60; and, finally, only much later in 
geological history (Jurassic or Cretaceous), they became 
like Fig. 59. This order of change is still retained in 
the embryonic development of the last introduced and 
most specialized order of existing fishes. The family his- 
tory is repeated in the individual history. 

Similar changes have taken place in the form and 
structure of birds’ tails. The earliest bird known—the 
jurassic Archeopteryx—had a long reptilian tail of 
twenty-one joints, each joint bearing a feather on each 
side, right and left (Fig. 62). 





bird, on the contrary, the tail-joints are diminished in 
number, shortened up, and enlarged, and give out long 
feathers, fan-like, to form the so-called tail (Fig. 63). 
The Archeopteryx’ tail is vertebrated, the typical bird’s 
non-vertebrated. This shortening up of the tail did not 
take place at once, but gradually. The Cretaceous birds, 
intermediate in time, had tails intermediate in struct- 
ure, ‘lhe Hesperornis of Marsh had twelve joints. At 


PROOFS FROM EMBRYOLOGY. 175 


first—in Jurassic—the tail is fully a half of the whole 
vertebral column. It then gradually shortens up until 
it becomes the aborted 








/ YWUWYWYV-- 
; ES MIVA 
organ of typical mod ‘, LE 
ern birds. Now, in 800 09) WM pf 
LW IN dddddiddddddttttz> 
embryonic _develop- Thr (SRE SS << 
ment, the tail of the WYSWUSSS 






modern typical bird ce WK 
Wik 


ON SASS G 
passes through all t, — 
these stages. At first 


the tail is nearly one 


Fig. 63.—-Tail of a modern bird. 


half the whole vertebral column ; then, as development 
goes on, while the rest of the body grows, the growth of 
the tail stops, and thus finally becomes the aborted or- 
gan we now find. ‘The ontogeny still passes through 
the stages of the phylogeny. The same is true of all 
tailless animals. The frog is tailed in the larval condi- 
tion, because its ancestors were tailed amphibians. Even 
man himself is endowed with a much more considerable 
tail, viz., eight or nine joints, in his early embryonic 
condition.* 

We have taken all our examples from vertebrates, 
but quite as many and as good examples might be found 
‘among articulates. Insects, in the larval state, are 
worm-like in form. Hence it is probable that the ear- 
liest progenitors of this class were worm-like. Again, 
some insects have aquatic larve. The progenitors of 


* Fol., “ Archives des Sciences,” vol. xiv, p. 84, 1885; “Science,” 
vol. vi, p. 92, 1885. 


176 EVIDENCES OF THE TRUTH OF EVOLUTION. 


these—in fact, of all insects—were probably aquatic. 
Crabs, in a larval condition, are long-tailed, and we 
know that the long-tailed crustaceans (Macrourans) pre- 
ceded the short-tailed (Brachyourans). Water-breathing 
animals preceded air-breathers ; the same is true in the 
ontogeny of the frog, of many insects, and, we might 
add, even of mammals. For the breathing of the fetus 
in utero is essentially by exposure of foetal blood to the 
oxygenated blood of the mother in a sort of gill-fringes 
(placental tufts). But why should we multiply exam- 
ples? The whole of embryology, in every department, 
is made up of examples of the same law. 

Illustration of the Differentiation of the Whole Animal 
Kingdom.—Finally, the law of differentiation in the evyo- 
lution of the whole animal kingdom may be well illus- 
trated by means of the different directions taken in the 
development of the eggs of all the various kinds of ani- 
mals. Suppose, then, we have one thousand eggs, rep- 
resenting all the different departments, classes, orders, 
families, etc., of animals. Many of these may doubtless 
be identified by form or size, or some other super- 
ficial character, as the eggs of this or that animal, 
but structurally they are all alike. At first, i. e., as 
germ-cells, they all represent the earliest condition of 
life on the earth, and the lowest forms of life now. 
If we now watch their development, we find that some 
remain in this first condition without further change. 
These we set aside. They are Protozoa. The remain- 
der continue to develop, but at first it would be 1m- 


PROOFS FROM EMBRYOLOGY. 177 


possible to say to which of the several departments or 
primary groups they each belonged. ‘Then, by cell-mul- 
tiplication, the original single cell becomes a cell-aggre- 
gate. It may be compared now to a compound proto- 
zoan, such as Foraminifera. The cell-aggregate then dif- 
ferentiates into layers, and forms, in fact, a two-layered 
sac called a gastrula. ‘This is the structure of some of 
the lowest ccelenterates, such as the hydra. Thus far all 
seem to go together. But now, for the first time, the 
primary groups are declared. If it be a vertebrate, for 
example, the most fundamental characters—the cere- 
bro-spinal axis, the vertebral column, and the double 
cavity, neural and visceral, are outlined. Suppose, now, 
we set aside all other departments, and fix our atten- 
tion on the vertebrates. At first we could not tell 
which were mammals, birds, reptiles, or fishes ; but after 
a while the classes are declared. We now set aside all 
other classes and watch the mammals. After a while the 
order declares itself. We select the ungulates. Then 
the family is declared, say the Hguide@ ; then the genus, 
Hquus ; and, lastly, the species, Cadallus.* 

The same would be true if we followed any other 
line of development, whether in vertebrates or in any 
other department. Observe, then, that, in following any 
one line as we have done, there is an increasing speciali- 


* Of course, this is a purely imaginary case. The conditions of de- 
velopment of the eggs of higher animals forbid continuous watching the 
process. Yet we do observe in different individuals all these stages in 
mammals as well as other animals. 


178 EVIDENCES OF THE TRUTH OF EVOLUTION. 


zation, and, if we followed all the lines, an increasing dif- 
ferentiation, like the branching and rebranching of a tree. 
Now, this is the type and illustration of what took place 
in the development of the animal kingdom. We con- 
clude that the animal kingdom appeared first as Proto- 
zoa, then as living cell-aggregates or compound proto- 
zoans, then as gastrula or two-layered sacs with oral 
opening. Then the great primary departments, unless 
we except the vertebrates, commenced to separate. ‘This 
took place before the primordial period ; for in the pri- 
mordial fauna we have all the departments, except verte- 
brates, already declared. ‘This completely explains why 
it is that we are able to trace homology only within the 
limits of each primary group. 

But the question has doubtless already occurred to 
the thoughtful reader, ‘‘ Why should the steps of the 
phylogeny be repeated in the ontogeny?” The general 
answer is doubtless to be found in the law of heredity— 
that wonderful law, so characteristic of living things. 
We have compared it to a brief recapitulation from mem- 
ory —the minor points, especially if they be also early, 
dropping out. Butcan we not explain it further? It 
is probable that we find a more special explanation in 
** the law of acceleration,” first brought forward by Prof. 
Cope. By the law of heredity each generation repeats 
the form and structure of the previous, and in the order 
in which they successively appeared. But there is a 
tendency for each successively-appearing character to ap- 
pear a little earlier in each successive generation ; and 


PROOFS FROM EMBRYOLOGY. 179 


by this means time is left over for the introduction of 
still higher new characters. Thus, characters which were 
once adult are pushed back to the young, and then still 
back to the embryo, and thus place and time are made 
for each generation to push on still higher. The law of - 
acceleration is a sort of young-Americanism in the ani- 
mal kingdom. If our boys acquire knowledge and char- 
acter similar to that of adults of a few generations back, 
they will have time while still young and plastic to press 
forward to still higher planes. 

Proofs from Rudimentary and Useless Organs.—These 
have to a large extent been anticipated under previous 
heads. ‘The tails of birds and the gill-arches of reptiles 
are rudimentary. The finger-bones of a whale’s paddle 
or a turtle’s flipper may be regarded as useless, at least 
so far as the exact number of constituent pieces is con- 
cerned ; for an extended surface, without visible joints 
or separate fingers, is all that is seen, and apparently all 
that is required. The splint-bones of a horse’s foot or 
the dew-claws of a dog’s foot are certainly useless. We 
have already, in speaking of modifications of structure 
and of embryonic conditions, given many examples of 
this kind, but it may be well to add some striking exam- 
ples with this special point in view. 

If different orders of existing mammals were indeed 
made by gradual modification of some generalized primal | 
form, then it is evident that these useless remnants of 
once useful parts would be most common in the most 
highly modified forms. Now, of all mammals, the 


180 EVIDENCES OF THE TRUTH OF EVOLUTION. 


whales are perhaps the most modified or changed from 
the original mammalian form—so much modified, in 
fact, that the popular eye scarcely recognizes them as 
mammals at all. Here, then, we might expect, and do 
indeed find, many examples : 

1. The baleen whales have no teeth, and no use for 
them. They have instead a wonderful armature of 
fringed whalebone plates (baleen), by means of which 
they gather their food.* Yet the embryo of the whale 
has a full set of rudimentary teeth deeply buried in the 
jawbone, and formed in the usual way characteristic of 
mammalian teeth—i. e., by an infolding of the epithelial 
surface of the gum—dut the teeth are never cut ; in fact, 
they reach their highest development in mid-embryonic 
life, and are again absorbed. Why, then, this waste of 
developmental energy ? Why should teeth be formed 
only to be reabsorbed without being cut ? The only con- 
ceivable answer is, because the ancestors of the whale, 
before the family of whales was fairly established, had 
teeth which were gradually, from generation to genera- 
tion, aborted, because no longer used, the baleen plates 
having taken their place. If whales were made at once 
out of hand as we now see them, is it conceivable that 
these useless teeth would have been given them? 

2. Again, many whales have rudimentary pelvic bones, 
but no hind-limbs. Why should there be pelvic bones, 


* These baleen plates are not modifications of teeth, as might at first 
be supposed, but rather of the transverse gum-ridges found on the roof 
of the mouth of many mammals, and conspicuous in the horse. 


PROOFS FROM EMBRYOLOGY. 181 


when the sole object of these bones is to act as a basis 
for hind-limbs? In some whales, for example the right 
whale, there are also rudiments of hind-legs, but these 
are buried beneath the skin and flesh, and therefore, of 
course, wholly useless. ‘The only explanation of these 
facts is that the ancestors of all the whales before they 
had become whales were quadrupeds, which afterward 
took to the water, and little by little the hind-legs, for 
want of use, dwindled away to the useless remnants 
which we now find. 

3. Again, whales seem to be hairless, yet rudimentary 
hairs are found in the skin. ‘Their organs of smell are 
rudimentary, but made on the pattern of those of mam- 
mals, not of fishes—i. e., they are air-smelling, not 
water-smelling organs. From all these, as well as many 
other facts, it is evident that the whales descended in 
early Tertiary times from some marsh-loving, powerful- 
tailed, short-legged, scant-haired quadruped by modifica- 
tions gradually induced by increasing aquatic habits. 

Examples of such rudimentary organs might be mul- 
tiplhed without limit. As might be expected, some are 
found even in man. Such, for example, are the muscles 
for moving the ear, necessary in animals but useless in 
man, and therefore rudimentary. Similarly useless in 
man are the scalp-muscle, used by aminals to erect the 
crest or bristles on the head, and the skin-muscle of the 
neck and chest, used by animals for shaking the skin of 
those parts. Most persons have lost the power of using 
these. For my part I can use them all—ear-muscles, 


182 EVIDENCES OF THE TRUTH OF EVOLUTION. 


scalp-muscle, skin-muscle—but they serve no useful pur- 
pose. 

Again, and finally, in man and many mammals we 
find a slender, worm-like appendage about three inches 
long, attached to the cecum of the large intestine. 
Anatomists and physiologists, under the influence of that 
philosophy which maintains that every part of the fear- 
fully and wonderfully made human frame was directly 
contrived to subserve some useful purpose, have puzzled 
themselves to find the use of this. It probably has no 
use ; on the contrary, it is a continual source of danger. 
If the human body had been made at once out of hand, 
it would not have been there. How came it, then? It 
is the rudimentary remnant of an organ—a greatly en- 
larged ceecum—which has served, and in some mammals 
still serves, a useful purpose. All these cases are sur- 
vivals; they are organs which, like many customs in 
society, have outlived their usefulness, but still continue 
by heredity. 

But why multiply examples? All along the track of 
evolution organs become useless by changes in the habits 
of their possessors. They are not, however, shed or 
dropped bodily at once. No; they are retained by 
heredity, but dwindle by disuse, more and more, until 
they pass away entirely. But even when they are en- 
tirely gone in the adult, they are often found still lin- 
gering in the embryo. They are among the most obvious 
and convincing proofs of the origin of ongeilig forms by 
derivation. 


CHAPTER VIII. 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION OF 
ORGANISMS. 


It is well known that the kinds of organisms found 
in widely-separated countries differ more or less con- 
spicuously. The traveler in Australia or in Africa finds 
all, the traveler in Europe nearly all, the animals and 
plants wholly different from those he has been accus- 
tomed to see at home. Even the visitor from the At- 
lantic to the Pacific coast, if he observes at all, will 
find nearly all organisms strange to him. The facts of 
geographical diversity of organisms are so numerous 
and complex that, at first sight, they seem utterly 
lawless. Only recently this subject has been redeemed 
from chaos and reduced to something like order and 
law by the light thrown upon it by the theory of evo- 
lution. We will give, in very brief outline, the most 
important facts, and then show how they may be ex- . 
plained. 

Geographical Faunas and Floras.—The group of ani- 
mals and plants inhabiting any locality, whether pecul- 
iar to that locality or not, is called, in popular lan- 


184 EVIDENCES OF THE TRUTH OF EVOLUTION. 


guage, its fauna and flora. But, in a true scientific 
sense, a fauna and flora is a natural group of animals 
and plants in one place, differing more or less conspic- 
uously from other groups in other places, and separated 
from them by physico-geographical boundaries, or by 
physical conditions of some kind. 'The members of 
such a group can only exist in certain harmonic rela- 
tions with external conditions, and with one another. 
These relations with one another are often complex and 
nicely adjusted, so that change in one term is propa- 
gated through the whole series of terms, giving rise 
often to the most unexpected results, until finally a 
new equilibrium is established. Thus, the destruction 
of certain insectivorous birds, in mere wanton sport, 
may give rise to the multiplication of insect pests, and 
this to the destruction of certain kinds of plants, and 
this to the diminution of certain herbivores, and this 
in its turn to the disappearance of certain carnivores. 
It is well known that the introduction of rabbits into 
New Zealand and Australia has produced the most un- 
expectedly disastrous effect upon certain crops, on ac- 
count of the absence of the fierce and active carnivores 
which keep in check their excessive multiplication in 
Europe. 

Now, among the physical conditions which limit 
faunas and floras, and separate them from each other, 
the most important and universal is temperature. 

Temperature-Regions—I{ we travel from equator to 
pole, we pass through mean temperatures varying from 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 185 


80° to 0°. This gives rise to a very regular zonal ar- 
rangement of plant-forms: 1. We have first a region 
in which palms and palm-like forms are abundant and 
characteristic, and which therefore may be called the 
region of palms. It corresponds with the tropic zone. 
2% We next have a region in which hard-wood folifer- 
ous trees are most abundant and characteristic; first 
mostly evergreens and then deciduous trees, and there- 
fore may be called the region of hard-wood forests, 
This corresponds with the temperate-zone. 3. Then we 
find a region characterized predominantly by pines and 
pine-like trees and birches, and may be called the 
region of pines. ‘This is the sub-Arctic region. 4. 
Then a region without trees, but only shrubs and 
summer plants. This is the Arctic region. 5. And, 
finally, an almost wholly plantless region of perpetual 
ice—the polar region. 

These regions are determined wholly by temperature, 
and therefore, in going up a mountain-slope to snowy 
summits, we pass through similar regions in smaller 
space. For example, in going from sea-level to the 
summits of the Sierra, 14,000 to 15,000 feet high, we 
commence in a region of predominantly hard-wood 
trees; but at 3,000 feet the forests become almost 
wholly coniferous, at 11,000 to 12,000 feet the vegeta- 
tion becomes shrubby, and at 13,000 feet we reach 
perpetual snow. 

We have taken plants first, because these, being 
fixed to the soil and incapable of voluntary seasonal 


186 EVIDENCES OF THE TRUTH OF EVOLUTION. 


migrations, are more strictly and simply limited by 
temperatare—i. e., the arrangement of different kinds 
in zones is more simple and conspicuous. But the 
same rule holds also for animals. In passing from 
equator to pole, animal kinds also change frequently, 
so that there are many temperature-faunas in which 
the animals are all very different. In both animals 
‘and plants, species, genera, families, etc., are limited 
by temperature. These are familiar facts; we recall 
them to the reader in order that we may base thereon 
a clearer definition of these limits. 

More Perfect Definition of Regions—1. The area 
over which any form spreads is called its range. Now, 
the range of a species is more restricted than that of 
a genus, because, when a species is limited by tempera- 
ture, another species of the same genus may carry on 
the genus. For the same reason the range of a family 
is usually greater than that of a genus, and so on for 
higher classification-groups. For example, pines range 
on the slopes of the Sierra from about 2,000 feet to 
11,000 feet, but not the same species. In ascending, 
we meet first the nut-pine (Pinus Sabiniana), then the 
yellow-pine (P. ponderosa), then the sugar-pine (P. 
Lambertiana), then the tamarack-pine (P. contorta), 
and last, the Pinus flexilis, ete. 

2. Where two contiguous temperature-regions come 
in contact, there is no sharp line between; on the con- 
trary, they shade gradually, almost imperceptibly, into 
one another, the ranges of species overlapping and in- 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 187 


terpenetrating, and the two species coexisting on the 
borders of their ranges. ‘This is represented by the 
diagram (Fig. 64), in which the horizontal lines repre- 
sent the north and south ranges 
of species of two groups, A and i ——3 — 
B, separated by the dotted line. 

3. Species also pass out 
gradually on the borders of a 
these ranges and others come | 





in gradually, so far as number Fra. 64, | 
and vigor of individuals are concerned. If aa’ and bo" 
(Fig. 65) represent the north and south range of two 
species, and 6 a’ their overlap or area of coexistence, 
then the height of the curves a and B will represent the 


oo eh LT. 


c a 6 
Fie, 65. 
number and vigor of the individuals in different parts 
of the range. 

4, While, therefore, there is a shading of contigu- 
ous groups into each other by overlap of species-ranges ; 
while there is also a gradual passing out of species so far 
as number and vigor of individuals is concerned, yet, in 
specific characters we observe usually no such gradation. 
Species seem to come in on one border with all their spe- 
cific characters perfect, remain substantially unchanged 
throughout their range, and pass out on the other border, 


still the same species. In other words, one species takes 
14 


188. EVIDENCES OF THE TRUTH OF EVOLUTION. 


the place of another, usually by substitution, not by 
transmutation. It is as tf species had originated, no 
matter how, each in its own region, and had spread in 
all directions as far as physical conditions and struggle 
with other species would allow. This important subject 
will be more fully discussed later. 

5. We have thus far spoken of species as limited by 
temperature alone, but they are limited also by barriers. 
If, then, there be an east and west barrier, such as a high 
mountain-range, or a wide sea or desert, there will be no 
shading or gradation of any kind, because the barrier 
prevents overlapping, interpenetration, and struggle on 
the margins. For example: The species north and south 
of the Himalayas, or north and south of Sahara, are 
widely different. It is, again, as if they originated each 
where we find them and spread:-as far as they could, but 
the physical barrier prevented mingling and shading. 

6. There are temperature-regions south as well as 
north of the equator. Now, although the climatic con- 
ditions are quite similar, the species of corresponding 
temperature-regions north and south are wholly differ- 
ent. It is, again, as if they originated where we find 
them, and were kept separate by the barrier of tropical 
heat between. If carried over, they often do perfectly 
well. 

Continental Faunas and Floras. 

If the land-surfaces were continuous all around the 
globe, there is little doubt that each temperature region 
with its characteristic species would also be substantially 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 189 


continuous. There would, it is true, be some local varia- 
tions dependent upon soil and humidity, etc., but sub- 
stantially the same species would exist all around. The 
distribution would be almost wholly zonal. But the in- 
tervening oceans are complete barriers to continental 
species. Hence we ought to expect, and do find, that the 
faunas and floras of different continents are almost to- 
tally different. 
Each apparently 
originated on its 
own continent, 
and did not 
spread to other 
continents, only 
because they 
could not get 
there. It is ne- 
cessary to explain 
this in more de- 





tail. Fic, 66.—Polar projection of the earth. 1, tropi- 
Fig. 66 repre- cal<% 2. temperate; 3, sub-arctic ; 4, arctic; 
: 5, polar regions. 
sents a polar view 


of the earth, showing the eastern and western conti- 
nents, and the five temperature zones already described. 
Now, if we examine the species in each region, com- 
mencing at the pole, we find that those of Nos. 5 
and 4 are almost identical all around. The reason is 
obvious. The continents come close together there, 
with ice-connection if not land-connection all around. 


190 EVIDENCES OF THE TRUTH OF EVOLUTION. 


There is but one circumpolar region. But, as soon as 
we come down to No. 3 and No. 2, the species on the 
two continents are nearly all different, because there 
is an impassable barrier between, either in the form of 
ocean or of Arctic cold. For example, the animals and 
plants inhabiting the United States are almost whol- 
ly different from those in Europe, not only in species, 
but even largely in genera and to some extent in families. 
There are some exceptions to this rule, but these are of 
the kind which prove the rule, or rather the principle on 
which the rule is founded. These exceptions are mainly 
of three kinds: 1. Introduced species.—All our weeds, 
many garden-plants, and many animal pests are of this 
kind. They were not found here when America was 
discovered, only because they could not get here; for, 
when brought here, they do so well that they often over- 
run the country and dispossess the native species, as we 
ourselves have done the Indians. 2. Hardy or else wide- 
migrating species. —Hardy species have wide range ; they 
may belong to No. 4 as well as No. 3. If so, they range 
down to No. 3 on both continents. Migrating birds, such 
as ducks and geese, etc., breed in summer in No. 4, and 
migrate southward in winter on both continents from the 
common circumpolar ground. 3. Alpine species.—It is 
a curious fact that species on tops of snowy mountains 
in temperate regions of the two continents are wonderfully 
similar, though so completely isolated. We are not yet 
prepared to discuss this point. We shall do so later. 
Suffice it to say now that it can be completely explained. 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 191 


In region No. 1 the continental diversity is still 
greater. Not only species and genera, but whole fami- 
hes and even orders, are peculiar to each continent. The 
great pachyderms—elephant, rhinoceros, hippopotamus— 
are peculiar to the Eastern; the edentates—sloths and 
armadillos—to the Western. The humming-birds, those 
gems of the forests, of which there are over four hun- 
dred species, and the whole cactus family, are peculiar 
to America, while the tailless monkeys are equally char- 
acteristic of the Eastern Continent. 

The continents do not come together again toward 
the south, and, therefore, as might be expected, the 
great difference between the two persists to the southern 
points. The faunas of the southern points of South 
America, Africa, and Australia are very different. 

Subdivisions of Continental Faunas and Floras.—Be- 
sides the subdivisions of continental faunas, north and 
south, determined by temperature as already explained, 
if there be in any continent an impassable barrier run- 
ning north and south, there will be a corresponding dif- 
ference in the species on the two sides, east and west. 
We give but one example: The North American Cordil- 
leras or Rocky Mountains, with their high ranges and 
desert plains, constitute a very great barrier between 
the eastern and western portions of the United States. 
Hence, we find an extraordinary difference between the 
species inhabiting California and those found in the east- 
ern portion of the country. Speaking generally, all the 
species and many of the genera are peculiar. The ex- 


192 EVIDENCES OF THE TRUTH OF EVOLUTION. 


ceptions, too, are significant. Leaving out introduced 
species, of which there are many, they are mostly strong- 
winged or widely-migrating birds, such as the turtle- 
dove, the turkey-buzzard, the bald eagle, and, of 
course, many water-birds. 

Special Cases.—If any body of land is widely sep- 
arated from all other lands by deep seas, we invariably 
find a corresponding peculiarity of its species. Thus, 
the species inhabiting Australia and Madagascar are per- 
haps the most peculiar in the world. We do not dwell 
further on these, because we will discuss them hereafter. 
There is a little group of very small islands—the Gala- 
pagos—about six hundred miles off the western coast of 
South America, and surrounded on all sides by deep sea. 
These islands are stocked with a collection of curious 
animals not found elsewhere on the surface of the earth ; 
but among them are no mammals at all. We might 
multiply examples without limit. Even the rivers empty- 
ing in the same sea sometimes have each its peculiar spe- 
cies of mussels. In the Altamaha River there are several 
species of unios—such, for instance, as the wonderful 
spinous unio—not found elsewhere. How came they 
there ? Howsoever they may have come there, they are 
now kept isolated there by barriers of land and of salt 
water. 

Many other curious details will come up in our dis- 
cussion of the origin of diversity. 

Marine Species.—Precisely the same principles apply 
here; but diversity in the case of marine species is 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 193 


perhaps less marked, and certainly less general, because 
of the universal oceanic connection. Open-sea species 
are therefore almost universal. But many marine spe- 
cies are confined to shallow water, and therefore to 
shore-lines. The species on the two shores of the same 
ocean, or the two coasts of the same continent, are dif- 
ferent, being isolated east and west by barriers of deep 
sea or of Jand, and north and south by temperature. 
Also about isolated lands, like Australia and Madagas- 
car, the species are pecular. 

Thus, then, species, genera, etc., are limited in every 
direction ; north and south by temperature, and in all di- 
rections by barriers, in the form of oceans, deserts, and 
mountain-chains. Add to these, peculiar climates and 
soils, and we see that, from this point of view, the 
whole surface of the earth may be divided and sub- 
divided into regions, sub-regions, provinces, etc. It 
would carry us too far to explain the primary and 
secondary divisions adopted by Mr. Wallace, and the 
somewhat different ones suggested by Mr. Allen. Our 
main object is to discuss the cause of this diversity, 
and especially to show the light shed upon it by the 
theory of evolution. We have only given a sketch of 
the facts sufficient for this purpose. 


Theory of the Origin of Geographical Diversity. 

It will be observed that all along we have assumed 
a sort of provisional theory. We have said in every 
case, it is as if organic forms originated where we find 


{94 EVIDENCES OF THE TRUTH OF EVOLUTION. 


them, and have gone thence wherever they could—as 
far in every direction as physical conditions and strug- 
gle with competing species would allow. This view 
has been formulated as the ‘‘theory of specific centers 
of origin.” There would be less objection to this as a 
first provisional theory did it not assume a supernatu- 
ral mode of origin. But, in the minds of those who 
hold it, it has usually assumed expressly or tacitly the 
form of ‘‘ specific centers of creation,” thus implying 
the immutability of specific types and the supernatu- 
ralism of specific origin (page 68). In this latter or 
usual form it completely fails to account for the facts 
given above. For, if this were the mode of origin, 
each species ought in every case to be perfectly adapt- 
ed to its own environment, and to no other. But, on the 
contrary, introduced species often fluarish better than 
in their own country, and better than the natives of 
their new homes. In the less objectionable form of 
‘“specific centers of origin,” without defining the mode 
of origin, it accounts well for many of the more obvi- 
ous facts of geographical diversity, as it now exists, but 
not all. According to this view, the amount of diver- 
sity ought to be in strict proportion to the complete- 
ness of isolation, or impassableness of the separating 
barriers ; but this is not exactly true. There is another 
element, not yet mentioned, which is just as important 
as impassableness, but which until recently has been 
left entirely out of account. This is the element of 
time—the amount of time since the barrier was set up, 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 195 


or during which it has continued to exist. These two 
elements, it is true, are closely connected with each 
other ; for, since all changes in physical geography have 
taken place very slowly—since barriers in the form of 
mountain-ranges and seas have increased by slow pro- 
cess of growth—it is evident that impassableness is, to 
some extent, a measure of time. But they are by no 
means in strict proportion. The one or the other may 
predominate. 

Now, this time-element connects geographical distri- 
bution with changes of physical geography and climate 
in geological times, and especially with the latest of 
these changes, viz., those occurring during the Glacial 
epoch. During that remarkable epoch extraordinary 
changes of climate, from extreme Arctic rigor to great 
mildness, enforced wide migrations of species southward 
and northward ; while concomitant changes of physical 
geography, by elevation of the earth’s crust over wide 
areas, opened highways between previously-isolated con- 
tinents, permitting migrations in various directions, and 
by subsequent depression again isolating the migrated 
species in their new homes. It is evident, then, that 
the recognition of the element of almost unlimited 
time at once introduces into the question of geographi- 
cal distribution the idea of evolution. If the study of 
geographical distribution, as it now exists, and as a 
part of science of physical geography, gave rise natu- 
rally to the theory of ‘‘ specific centers of origin,” the 
study of the same, in connection with geological time, 


196 EVIDENCES OF THE TRUTH OF EVOLUTION. 


and as a part of geological science, now demands its 
explanation by the theory of evolution. 

It must be borne in mind, then, that geographical 
diversity of organisms is not a question of the present 
epoch only. ‘There has been geographical diversity in 
every previous geological epoch ; it 1s, therefore, a ques- 
tion of geology as well as of biology. It is probable, 
however, that diversity has increased with the course 
of geological times, and is greater now than ever be- 
fore. In other words, in the evolution of the organic 
kingdom, the law of differentiation has prevailed here, 
as in other departments of biology. A clear statement 
of the causes of the present distribution of organisms 
must embrace also the causes of geographical diversity 
generally. We give, therefore, at once a brief state- 
ment of what seems to us the most probable view, and 
shall then proceed to show how it explains the present 
distribution. 

Most Probable View of the General Process.—Bear- 
ing in mind, then, this time-element, the phenomena 
of geographical diversity are best explained by the fol- . 
lowing suppositions: 1. A gradual progressive move- 
_ ment (evolution) of the organic kingdom, marching, 
as it were, abreast, at equal rate along the whole line— 
1. €., in all parts of the earth, and throughout all geo- 
logical times, under the action of all the forces or fac- 
tors, and following all the laws, of evolution already ex- 
plained (pages 19 and 73). If this were all, there would 
be no geographical diversity, although organic diversity 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 197 


might be as great as it is now. ‘There would be dif- 
ferentiation of forms and structure everywhere, but no 
differentiation of groups in different localities. 2. 
Under the influence of different conditions in different 
places, more or less isolated from one another by cli- 
matic or physical barriers, the onward movement (evo- 
lution) of organic forms takes different directions and 
different rates, and gives rise to local groups, which 
become more and more differentiated, without limit as 
time goes on. This element, acting by itself through- 
out all geological times, would ere this have produced 
an extreme geographical diversity, such as does not any- 
where exist. 38. From time to time, at long intervals, 
extensive changes of physical geography and climate, 
produced by crust elevations, partly enforce by change 
of temperature, and partly permit by opening of gate- 
ways, extensive migrations and dispersals of species, by 
which mingling and struggle for life and final readjust- 
ment takes place, and extreme diversity is prevented. 
Such mingling of different faunas and floras on the same 
ground, and the severe struggle for life that thus ensues, 
and the survival of the fittest in many directions, are, as 
already shown, among the most powerful factors of evo- 
lution. They tend to increase organic diversity, but to 
diminish geographical diversity. 4. At the close of such 
great periods of change as indicated in the last, by con- 
trary movement of the earth-crust—i. e., subsidence— 
new barriers are set up and new isolations are produced, 
and the process of divergence again commences and 


198 EVIDENCES OF THE TRUTH OF EVOLUTION. 


increases steadily so long as the barriers continue to 
exist. 

Now, the last of these periods of great changes and 
extensive migrations, and subsequent isolations, was the 
Glacial epoch. It was this epoch, therefore, which 
mainly determined the present geographical distribu- 
tion of species. Thus, the present distribution is a key 
to the directions of the last great migrations, and there- 
fore to the nature of the changes in physical geogra- 
phy and climate which then occurred ; and, conversely, 
the character of these changes, determined in other 
ways, furnishes the only key to the present distribution 
of species. 

Before applying the foregoing principles in the ex- 
planation of special cases, it may be well to give a very 
brief outline of the condition of things during the Gla- 
cial epoch. 

In America, during this epoch, by increasing cold 
the southern margin of the great northern ice-sheet 
crept slowly southward, until it reached the latitude of | 
about 38° to 40°. Arctic species were thus driven 
southward slowly, from generation to generation, until 
they occupied the whole of the United States, as far 
as the shores of the Gulf, while temperate species 
were forced still farther south, into Central and South 
America. This period of extreme rigor and southward 
migration was followed by a period of great mildness, 
during which the ice and its accompanying Arctic con- 
ditions retreated northward, followed by Arctic species. 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 199 


More than one advance and retreat, apparently, oc- 
curred during this time. Again, during the same time, 
brought about by northern elevation, there was broader 
connection than now exists between North and South 
America, and free migrations between, in both direc- 
tions, enforced by extreme changes in temperature. 
Also, during this or previous time, there were broad 
connections between North America and Asia, in the 
region of Behring Strait, and between America and 
Kurope, in high-latitude regions, and extensive migra- 
tions of faunas and floras between were thus permitted. 
The necessary result: of all these migrations of species, 
partly enforced by changes of climate, partly permitted 
by opening of gateways since closed, was exceptionally 
rapid changes in organic forms. This was the result of 
two causes: First, the severer pressure of a changing 
physical environment ; and, second, a severer struggle 
for life between the natives and the invaders. 

In Europe, during the same time and from similar 
causes, there were at least three or four different faunas 
struggling together for mastery on the same soil. First, 
there were the Pliocene indigenes, who had, if any, 
preemption right to the soil; second, invaders from 
Arctic regions, driven southward by increasing cold ; 
third, invaders from Asia, permitted by the removal 
of the old sea-barrier which once extended from the 
Black Sea to the Arctic, and of which the Caspian and 
Aral are existing remnants, and thus opening a gateway 
for migration which has remained open ever since; 


900 EVIDENCES OF THE TRUTH OF EVOLUTION. 


fourth, invaders from Europe and Asia into Africa, 
and sometimes back again into Europe, by opening of 
gateways through the Mediterranean, which have been 
since closed. One of these highways was through Gib- 
raltar, and one from Italy to Africa through Sicily. 
As in America, so here, in even greater degree, the 
severe pressure of changing environment and the severe 
struggle for life produced rapid changes of organic 
forms. Many species were destroyed; others saved 
themselves by modifications adapted more perfectly to 
the changed conditions. There is little doubt that 
man came into Europe with the Asiatic invasion, and 
was one of the principal agents of change, especially 
in the way of destruction of many old forms. 

Such is a very brief outline of the last great geo- 
logical change and its general results. Being the last, 
this one has left the strongest and most universal im- 
press on the present geographical distribution. But 
similar changes by crust oscillations, if not also by 
extreme changes of climate, have repeatedly occurred 
in geological times, and some of the most remarkable 
geographical faunas and floras are the result of these | 
earlier geological changes. We will now give a few 
examples illustrating these principles: 

1. Australia is undoubtedly more peculiar in its 
fauna and flora than any other known country. Not 
only are all its species peculiar, not found elsewhere 
on the face of the earth, but its genera, its families, 
and even many of its orders of animals and plants, are 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 201 


also peculiar. These facts are so familiar that it is 
unnecessary to dwell on them. I need only mention, 
among plants, the whole of the simple-leaved acacias, 
already mentioned on page 86, of which there are so 
many species, and the whole family of the eucalyptids, 
of which there are several hundred species. Among 
animals I need mention only the order of monotremes, 
or egg-laying mammals, and nearly the whole order of 
marsupials, or pouched animals, of which there are 
over two hundred species. On the other hand, the 
true typical mammals are entirely absent, with the ex- 
ception of a few bats and a few rats, which have evi- 
dently been accidentally introduced from abroad. 

Another very noteworthy fact, which must be taken 
in connection with the last, is that Australian forms 
are far less advanced in the race of evolution than 
those of any other country—i. e., that many old forms 
which have long ago become extinct elsewhere are still 
retained there. A few examples will suffice. The mar- 
supials just mentioned are an old form once universally 
distributed, but now nearly extinct everywhere, except 
in Australia; the cestracion, or Port Jackson shark, 
and the ceratodus, are Palewozoic and Mesozoic forms 
retained only in Australia. 

What is the explanation of these remarkable facts ? 
We find the sufficient answer in the fact that Australia 
has been long isolated from all other countries. While 
geographical changes in geological times have mingled 
more or Jess the organic forms of other countries, and 


902 EVIDENCES OF THE TRUTH OF EVOLUTION. 


the sharp struggle for life has produced more rapid ad- 
vance and the production of many new and higher forms 
better armed for the battle of life, Australia has remained 
isolated from competition, and therefore comparatively 
unprogressive. 

Can we tell when Australia was finally isolated ? Ap- 
proximately we can. The class of mammals is divided 
into two groups, which differ widely from each other ; 
80 widely, that they are called sub-classes. ‘These are 
placental mammals, or true typical mammals, and non- 
placental or reptilian mammals. The non-placentals in- 
clude only the marsupials and the monotremes (ornitho- 
rhyncus and echidna). ‘The monotremes actually lay 
eggs and incubate them. In the marsupials the embryo 
has no placental connection with the mother, and is 
born in a very imperfect condition, utterly unfit for in- 
dependent life, and placed in the pouch (marsupium), 
and permanently attached there to the teat until it is 
capable of independent life ; after which only it volunta- 
rily nurses like other new-borns. In other words, the | 
gestation commenced in the womb is completed in the 
pouch. The uterine gestation in the opossum is only 
seventeen days, while the marsupial gestation is about 
two and a half months. In a kangaroo seven feet high 
in sitting position the embryo at birth is only one inch 
long—a pink, hairless, almost amorphous mass. The 
monotremes are pure oviparous animals, like birds and 
reptiles. The marsupials might well be called semi- 
oviparous. In pure egg-layers the whole embryonic de- 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 9203 


velopment is outside of the body ; in pure young-bearers 
the whole is within the body; in marsupials it is partly 
within and partly without. Now—l. The monotremes 
are found nowhere but in Australia and the neighbor- 
ing New Guinea. 2. The marsupials are also all con- 
fined to the Australian region, except a few oppossums 
in America. 3. There are some two hundred and thir- 
ty species of non-placentals in the Australian region. 
4, As already said, there are no true mammals at all in 
Australia, except a few bats and rats which have come 
accidentally from abroad. 5. But non-placentals existed 
abundantly in Mesozoic times everywhere, both in Eu- 
rop-Asia and in America, while true mammals did not 
appear at all on the surface of the earth until the Zer- 
tiary, when they almost immediately became very abun- 
dant everywhere, except in Australia. vidently, there- 
fore, Australia was isolated before the Tertiary. The 
enormous difference between its fauna and flora and 
those of other countries is due to at least three things: 
1. So long an isolation necessarily produced great diver- 
gence of forms. This alone, however, would not affect 
the grade of organization. 2. Saved from wide migra- 
tions, and especially invasions from Eurasia, the great 
field of competitive struggle, it was left far behind in 
the race of evolution. Hence many of its forms are ar- 
chaic ; its mammalian fauna, for instance, 1s still in the 
Mesozoic stage. 3. Its distance from other large conti- 
nents is so great that accidental colonization has been 


very slight, only extending to a few bats and a few rats. 
15 


904 EVIDENCES OF THE TRUTH OF EVOLUTION. 


I stop a moment to insist on the effect of competitive 
struggle in developing organic forms strong for the battle 
of life. Ofall the continents, Eurasia has been the scene 
of most frequent geological changes, and therefore the 
arena of fiercest competitive struggle through wide and 
frequent migrations. Eurasian species, therefore, are 
the strongest of all. They have conquered wherever 
they have gone. Species in isolated regions are usually 
the weakest. The great moas and the dodo could not 
have continued to exist unless protected in a sort of 
bomb-proof. Kangaroos would now be quickly extermi- 
nated by the introduction of fierce Eurasian carnivores. 

2. Africa.—The fauna of that part of Africa north 
of Sahara is essentially Mediterranean—i. e., a sub-group 
of the Eurasian. Sahara, rather than the Mediterranean 
Sea, is the true intercontinental barrier. The true Afri- 
can region, therefore, is south of Sahara. Now, accord- 
ing to Mr. Wallace, whom I mainly follow here, the true 
African mammalian fauna consists of two very different 
groups of animals. ‘The one is a group of very small, 
curious animals, mostly low forms of insectivores and 
lemurs, very peculiar to this region, though more resem- 
bling those of Madagascar than of any other region ; the 
other is a group of large and powerful animals which 
dominate the region. These latter are similar to, though 
not identical with, those which inhabited Eurasia in Pli- 
ocene times. The great carnivores, pachyderms, and ru- 
minants of the region are examples of this group. Now, 
the explanation of these facts is as follows: The indige- 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION, 9205 


nes of Africa are the animals of the first group. Africa, 
in Tertiary times, was isolated from the great field of 
combat, Eurasia, and therefore its animals were small, of 
low grade, and peculiar. During later Tertiary (Plio- 
cene) times, then, Africa was inhabited by animals of the 
first group, while EHurasia was dominated by animals of 
the second group. ‘These two groups were then sepa- 
rated by the Desert of Sahara, or else by a sea in that re- 
gion. Some time during the Glacial epoch geographical 
changes removed this barrier, and climatic changes drove 
the Eurasian animals southward into Africa, where, find- 
ing congenial climate, they took possession of the conti- 
nent, dominating the feebler natives. Subsequently they 
were isolated there by the formation of the desert, and 
the process of divergence commenced, and has gone on 
to the formation of many new forms. Meanwhile the 
change, partly by extinction and partly by modification, 
has gone on still more rapidly in Eurasia, but in a dif- 
ferent direction. Hence, Africa is regarded as one of the 
primary faunal regions. 

3. Madagascar. — This, next to the Australian, is 
probably the most peculiar faunal region known. There 
is probably not a single mammalian species found there 
which is known to occur anywhere else. It is remarkable 
also as the principal home of that strange, generalized, 
ancient form of monkeys—the lemurs. And yet its ani- 
mals, though very different, have a distant resemblance to 
those of Africa; not, however, to the present dominant 
type, but to those we have called the indigenes. Not 


206 EVIDENCES OF THE TRUTH OF EVOLUTION, 


one of the northern invaders is found there. The ob- 
vious conclusion from these facts is, that Madagascar 
was formerly united with Africa, and both were occupied 
by the same mammalian fauna (which may be called Af- 
rican indigenes, although they were considerably differ- 
ent from their descendants of the present day), but be- 
came separated before the northern invasion. The effect 
of this invasion was to hasten the steps of change in the in- 
digenous fauna of Africa, partly by extermination, partly 
by modification, while the isolated portion in Madagascar 
went on at the usual slow rate of change in isolated re- 
gions. ‘The time since the separation (which was cer- 
tainly during the Tertiary period) has been sufficiently 
long to produce very great divergence in both, but espe- 
cially in the African indigenes. In the fauna of Mada- 
gascar, therefore, we have a nearer approach to the origi- 
nal fauna of both. On account of this long isolation, we 
have here many ancient types which are extinct else- 
where. The lemurs are such an ancient type. These are 
a wonderfully-generalized type of monkeys—a connect- 
ing link between monkeys and other mammals, especially 
insectivores. As might be supposed, from the law of dif- 
ferentiation, already explained (page 11), they are the 
earliest form, the progenitors, of monkeys. In fact, in 
early Tertiary times, they were found not only in Africa 
and Madagascar, but all over the earth, as the only rep- 
resentatives of the monkey family. The true monkeys 
were not introduced until the mid-Tertiary. In Eura- 
sia and in America (which at that time was probably 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 207 


connected with Eurasia) wide migrations and frequent 
conflicts of faunas produced comparatively rapid evolu- 
tion of new and higher forms, while in isolated Africa 
old types continued until the invasion. Madagascar was 
spared this invasion, and therefore old types are still pre- 
served there. At present, at least three quarters of all 
lemurs are confined to Madagascar, although a few spe- 
cies are still found in Africa and in the great Hast Indian 
islands. 

4, Island-Life.—Mr. Wallace has divided islands into 
two kinds, continental and oceanic islands. The division 
is undoubtedly a good one, although we may not always 

be able to refer an example with certainty to the one or 
the other class. Continental islands are those on the bor- 
ders of continents, and separated from the latter only by 
shallow water. Oceanic islands are those, usually very 
small, found in the midst of the ocean, with abyssal 
depth all about. ‘Continental islands may be regarded as 
appendages to the neighboring continent—as outliers of 
continents separated by submergence, and have, in fact, 
been thus formed. Oceanic islands have been formed 
geologically recently by volcanic action building up from 
the sea-bottom. Continental islands have a continental 
structure—i. e., they are composed of stratified as well 
as of igneous rocks. Their structure is a record of 
geological history, like that of the neighboring continent. 
Oceanic islands are composed wholly of volcanic rocks ; 
or, if there be any stratified rocks, these are only of the 
most recent date. As examples of continental islands we 


208 EVIDENCES OF THE TRUTH OF EVOLUTION. 


have New Zealand as an appendage of Australia, the 
great East Indian (Borneo, Java, Sumatra, etc.) and the 
Japanese Islands, etc., as appendages of Asia; the British 
Islands, appendages of Europe ; the West Indian Islands, 
appendages of America; Madagascar, an appendage of 
Africa, etc., etc. As examples of oceanic islands we 
have the Azores and Bermudas in the Atlantic, and the 
Polynesian islands in mid-Pacific. 

a. Continental Islands.—Now, the fauna of conti- 
nental islands, as might be expected from the mode of 
origin of these islands, is similar to, though not identical 
with, that of the neighboring continent; the amount of 
difference being in proportion to the length of time since 
they were separated and the width of the separation. 
Madagascar, for example, has been long separated from 
its parent continent, and by a wide and deep channel. 
Its fauna, therefore, differs greatly from that of Africa, 
although resembling it more than that of any other 
country. The separation of New Zealand from Aus- 
tralia has been not quite so long, and the divergence, 
therefore, is not so great. These two will be sufficient 
illustrative examples of long separation, and therefore 
of great differentiation of forms. 

On the other hand, the British Isles are an excellent 
example of comparatively recent separation. These isles 
have probably been several times united and separated 
from Europe, but we are here concerned only with the 
more recent. They are now separated from the conti- 
nent and from one another only by shallow seas. An 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 209 


elevation of less than six hundred feet—geologically a 
very small change—would bare the bottoms of the Irish 
and English Channels and the North Sea, and connect 




























































































































































































































































































































































































































































































FiG. 67.—Map of outline of coast of Western Europe, if elevated 600 
feet (after Lycll). 


~ 


210 EVIDENCES OF THE TRUTH OF EVOLUTION, 


these islands with one another and with the continent 
(Fig. 67). Now, it is well known that there were dur- 
ing the Glacial epoch, and subsequently, several oscilla- 
tions of level sufficient to connect and separate these 
islands. In the mid-Glacial epoch the British Islands, 
by submergence, were nearly obliterated, being reduced 
to an archipelago of small islets representing the high 
mountains of Wales and Scotland. The Pliocene fauna 
and flora were, therefore, largely exterminated. During 
the close of that epoch they were elevated above the 
present condition and broadly connected with the con- 
tinent (Fig. 67), and the newly-exposed land was taken 
possession of by European species, man among the num- 
ber. Still later—i. e., at the beginning of the present 
epoch—the islands by subsidence were again separated, 


but not widely, from the continent. This is the condi- . 


tion now. What, then, was the result? 1. The fauna 
and flora of the British Isles are substantially the same, 
but less rich in species than that of Continental Europe, 
some of the Huropean species being wanting. This shows 
that the last connection was not a long one ; the coloni- 
zation had not been completed before re-isolation. 2. 
This poverty of species is more conspicuous in Ireland, 
because colonization is progressive in space as well as in 
time. Some species had not reached so far when Ireland 
was re-isolated from England. The conspicuous absence 
of snakes, for example, is thus accounted for, There is, 
we all know, another theory to account for this, but we 
prefer the natural one. 3. The difference between Brit- 


~ 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 911 


ish and European fauna and flora is very small, it is 
true, but there is some difference, varietal if not specific. 
The reason is, that the time since separation is too small 
to produce much divergence, and the width of the exist- 
ing barriers not great enough to prevent colonization by 
accidental causes. 

The continental islands of the southern coast of 
Asia are good examples of an intermediate condition as 
to the length of time since separation, and of the 
consequent degree of differentiation of the faunas and 
floras. 

Coast-Islands of California.—We give one more exam- 
ple, and dwell upon it a little, because it occurs on our 
own coast. 

The recent studies of Mr. E. L. Greene on the flora 
of the islands off the coast of California have brought to 
light some facts which are an admirable illustration of 
the principles laid down above. 

On looking at a good map of California, any one will 
observe eight or ten islands, some of them of consider- 
able size, strung along the coast from Point Conception 
southward, and separated from the mainland by a sound 
twenty to thirty miles wide. They are in structure true 
continental islands—outliers of the mainland separated 
by a subsidence of a few hundred feet. Moreover, the 
date of their separation is known. ‘They were certainly 
connected with the mainland during the later Pliocene 
and early Quaternary, for bones of the mammoth, char- 
acteristic of that time, have been found on one of 


912 EVIDENCES OF THE TRUTH OF EVOLUTION. 


them.* They were therefore separated during the Gla- 
cial epoch. 

The main peculiarities of the flora of these islands are 
the following : 

1. Out of nearly three hundred species of plants gath- 
ered by Mr. Greene, about fifty are wholly peculiar to 
these islands. 2. Of the remaining two hundred and fifty 
species, nearly all are distinctively Californian. In other 
words, the distinctively Californian forms are very abun- 
dant, while the common American forms are rare—i. e., 
the island flora is distinctively Californian, with many 
peculiar species added. 

I explain these facts as follows: The whole coast- 
region of California is geologically very recent, having 
emerged from the sea as late as the beginning of the Pli- 
ocene epoch. As soon as emerged it was of course colo-. 
nized from adjacent parts. Since that time its peculiar 
flora has been formed by gradual modification. ‘The en- 
vironment has been sufficiently peculiar, the isolation 
sufficiently complete, and the time sufficiently long, to 
make a very distinct group of organisms. It is one of 
Mr. Wallace’s primary divisions of the Ne-arctic region. 

During late Pliocene and early Quaternary times, as 
already said, the islands were still a part of the mainland, 
and the whole was occupied by the same species, viz., 
the distinctively Californian species now found in both, 
together, as I suppose, with the peculiar island species. 


* “ Proceedings of the California Academy of Science,” vol. v, p. 152. 
1873. 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 913 


During the oscillations of the glacial times the islands 
were separated by subsidence of the continental margin. 
Simultaneously with this subsidence, or subsequently 
thereto, came the invasion of northern species, driven 
southward by glacial cold. Then came the mingling of 
invaders with natives, the struggle for mastery, the ex- 
termination of many forms—viz., the peculiar island spe- 
cies—and the slight modification of others, and the final 
result is the California flora of to-day. But the island 
flora was spared this invasion by isolation. Therefore 
the invading species are mostly wanting, the distinctive 
island species were saved, and the result is the island flora 
of to-day. The island flora, therefore, somewhat nearly 
represents the Pliocene indigenes of both. 

It will be observed that this case is somewhat like 
that of Madagascar, but with a characteristic difference. 
In the case of Madagascar, the separation has been long. 
The extreme peculiarity of its fauna is the result partly 
of progressive divergence and partly of many forms saved 
by isolation. In the case of the coast-islands of Califor- 
nia, the time has not been long enough for any great 
divergence by modification. The peculiarity of its spe- 
cies is due almost wholly to species saved by isolation.* 


b. Oceanic Islands.—We have seen that faunas and 





floras of continental islands are somewhat similar to those 
of the neighboring continent, though with varying degrees 
* For fuller discussion of this subject, see “ Bulletin of the Califor- 


nia Academy of Science,” No. 8, 1887, and “ American Journal of Sci- 
ence,” for Dec., 1887. : 


914. EVIDENCES OF THE TRUTH OF EVOLUTION. 


of difference—the amount of difference, or divergence by 
evolution, being in proportion to the amount of time and 
the impassableness of the separating barriers. But ocean- 
ic islands have never been connected with any continent. 
They are new land formed in the midst of the ocean by 
volcanic action. When they first appeared they were, of 
course, without inhabitants of any kind, animal or vege- 
tal. How were they peopled? We answer by waifs 
from here and there—by castaways from other lands. 
The dominance of particular kinds will depend on the 
direction of winds and currents, bringing from some 
Jands more than others, and upon the kinds of animals 
or seeds of plants most liable to be successfully carried 
across wide seas. ‘Their faunas and floras, therefore, are 
characterized by a mixture of species resembling, though 
not usually identical with, those of various lands, with a 
predominance of those of some one land, and by the 
singular and complete absence of mammals and amphib- 
ians, these being unlikely to be transported by floating . 
timber, as are small reptiles and insects, ete. Among 
mammals, however, there is a significant exception in 
favor of bats, the reason being both their power of flight 
and their habit of concealment in hollow trees, etc. ‘To 
this explanation, however, we must add that divergence 
by isolation will meanwhile go on in proportion to time. 
The Azores, for example, have been peopled from Eu- 
rope, Africa, and America, but mostly from Europe, on 
account of the prevailing winds and currents being favor- 
able to colonization from that direction. There are 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 9215 


many curious peculiarities in the species, however, be- 
cause colonization is very slow, and divergent variation 
has been going on pari passu. ‘The Bermudas, on the 
other hand, have been colonized mainly from America, 
because of the current of the Gulf Stream. 

These few examples are sufficient for our purpose, 
which is only to illustrate the causes of geographical dis- 
tribution. If any one desires to pursue this interesting 
subject, we would refer him to that most fascinating 
book, Mr. Wallace’s ‘‘ Island-Life.” 

5. Alpine Species—These afford an admirable illus- 
tration of the fact that in isolated faunas and floras the 
amount of difference is proportioned not only to the 
completeness of isolation, but also and mainly to the 
time of isolation. 

It is well known that Alpine species—i. e., those spe- 
cies inhabiting the region bordering the perpetual snow 
of lofty mountains—are very similar to one another, even 
in the most distant localities, where their isolation from 
one another is as complete as possible ; as, for example, in 
the high Alps of Europe, the high mountains of Colo- 
rado and California. Why is this? We find the key to 
this mystery in the additional fact that they are similar 
also to Arctic species. A somewhat full explanation is 
here necessary. 

During Miocene times, magnolias and taxodiums (bald 
cypress), like those in forests and swamps of Carolina 
and Louisiana, and sequoias and libocedrus like those 
now in California, and many other temperate - region 


916 EVIDENCES OF THE TRUTH OF EVOLUTION. 


forms of plants, grew abundantly in Greenland, and north- 
ward certainly to 75° north latitude. At that time there 
could not have been any perpetual polar ice, and there- 
fore no Arctic species, unless on high mountains in polar 
yegions. In Pliocene times perpetual polar ice, and there- 
fore Arctic species, probably commenced to appear. As 
the cold of the Glacial epoch came on and increased in 
severity, the polar ice extended southward as a general 
ice-sheet, until it reached in America 40° and in Europe 
about 50° north latitude. In the United States its mar- 
gin can be traced as a distinct moraine through Long 
Island, middle New Jersey, middle Pennsylvania; thence, 
less distinctly, following the Ohio River, crossing the Mis- 
sissippi; thence following the Missouri, on its south side, 
into Montana. By the increasing cold, Arctic species 
were driven slowly southward, generation after genera- 
tion, until they occupied the whole of the United States 
to the Gulf, and the whole of Europe to the Mediterra- 
nean. As these species on the two continents came from / 
a common home in polar regions, they were similar to 
one another, except in so far as some slight divergent 
modification may have been produced during their south- 
ward travel. When the glacial rigor declined, and the 
ice-sheet gradually retreated to its present position, Arc- 
tic species, following the snow-edge, went also north- 
ward, on both continents, to their present home in polar 
regions. But there was an alternative way of migration 
left open which was embraced by certain plants and in- 
sects. While on both continents most individuals went 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 217 


northward, some of them went upward, following the snow- 
edge into high mountains, and were left stranded there. 
Thus it has come to pass that the plants and insects of high 
mountains in temperate regions of different continents, 
though so widely separated and impassably isolated, are 
extremely similar to one another. But, though similar, 
they are rarely identical. The time has been long enough 
for some but not very great divergent modification. It 
is impossible to conceive a more beautiful illustration of 
the principles we have been trying to enforce. 


Thus, then, undoubtedly all the phenomena of geo- 
graphical distribution of species are most rationally 
explained on the principle of slow evolution - changes, 
different in different places, and increasing with the time 
of isolation and its completeness. 

Objection—The only objection which can be raised 
against this view is the manner in which contiguous geo- 
graphical faunas and floras pass into one another when 
they are limited not by barriers but by temperature. In 
passing from equator to poles, over continuous land, 
we of course pass through many successive faunas and 
floras, limited wholly or mainly by temperature. Now, if 
species are indeed indefinitely modifiable, then on the bor- 
ders of contiguous faunas or floras, where one species dis- 
appears and another closely allied but adapted to a colder 
temperature takes its place, the one species (say the anti- 
evolutionists) ought to be gradually transmuted into the 
other, so that all the gradations may be traced. But this 


918 EVIDENCES OF THE TRUTH OF EVOLUTION, 


is certainly not usually the fact. On the contrary, a 
species may indeed pass out gradually, and another come 
in gradually, so far as number and vigor of individuals 
are concerned ; but, in specific character, they may 
be said, usually at least, to come in suddenly, with all 
their characters perfect, remain unchanged throughout 
their whole range, and pass out suddenly at its borders. 
Another species takes its place, overlapping in range and 
coexisting on the borders of both; this also continues 
unchanged, as far as it goes, and so on. The change 
from one fauna to another is apparently not by transmu- 
tation of one species into another by gradations, but by 
substitution of one perfect species for another perfect 
species. Asa broad general statement, the condition of 
things is precisely such as would be the case if specific 
types were substantially immutable by physical con- 
ditions, but were originated in some inscrutable way 
(created) in the regions where we now find them, and 
have spread in every direction as far as physical condi- 
tions and struggle with other species would allow them— 
their ranges therefore interpenetrating and overlapping 
one another on their borders. 

Two characteristic examples will make our meaning 
clear. ‘There is not a more characteristic tree known 
than the sweet-gum, or liquidambar. This tree grows 
from the borders of Florida to the shores of the Great 
Lakes. It may indeed be most numerous and vigorous 
somewhere in the middle region, and may die out grad- 
ually in number and vigor of individuals on the borders 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 219 


of its range, but in specific character it is substantially 
the same throughout, easily recognizable by its dense 
wood, its winged bark, its five-starred leaf, its spinous 
burr, and its fragrant gum. Physical conditions may 
diminish its number and vigor, and limit its extension, 
but seem powerless to essentially modify its specific char- 
acter. It seems to give up its life rather than change 
its nature. 

Another striking example: The sequoias (redwood 
and big-tree) are entirely confined to California, and 
there are only two species now existing, viz., the redwood 
GS. sempervirens) of the Coast Ranges, and the big-tree 
(S. g:gantea) of the Sierra Nevada. Doubtless they are 
most numerous and vigorous somewhere in the middle 
of their range, and die out gradually in number and 
vigor on the borders north and south, being replaced 
there by other genera better adapted to the physical 
conditions ; but in specific character they remain essen- 
tially unchanged throughout. They are everywhere 
the same—easily recognizable by wood, bark, leaf, and 
burr. Both in this case, and in the previous one of 
the sweet-gum, it is as if they were created perfect in 
their present localities, and have spread in all directions 
as far as physical conditions and the struggle with other 
competing species would allow ; but physical conditions 
seem powerless to change them into any other species 
by adaptive modification. 

Answer.—We have, we believe, stated the objection 


fairly, The answer is, that the elements of ¢ime and 
16 


220 EVIDENCES OF THE TRUTH OF EVOLUTION. 


of migrations have not been taken into the account. In 
fact, this objection was conceived and formulated before 
the idea of geological time was fully assimilated by the 
human mind, and our theories of origin adjusted to it. 
If these species did indeed originate where we now find 
them, and in the present geological epoch, the argument 
might at least be entertained ; but this is not the fact. 
We know something of the geological history of all 
these species, and the history of the migrations of some 
of them. We know that sweet-gums were abundant 
and of many species in the United States in Tertiary 
times, and all have become extinct except this remnant. 
Whatever of modifications there were must be looked 
for at or about the time of its origin in Tertiary times, 
not now. Species, like individuals, are plastic only 
when young. This one has already become rigid, and 
all the more so as it is a remnant widely separated from 
other species. For competition is strongest and most 
effective with nearest allies. Present species are mostly 
isolated remnants—terminal twiglets of the tree of life. - 
Twiglets are of course widely separated at their visible 
ends. Their points of union with other twiglets must 
be sought below. 

In the case of the sequoias, we know something also 
of the history of their migrations. In Miocene times 
they were abundant, and of many species in circumpolar 
regions. Some twenty-four species of fossil sequoias 
dre known, fourteen of which are Tertiary. By the 
cold of the Glacial epoch they were driven slowly south- 


PROOFS FROM GEOGRAPHICAL DISTRIBUTION. 9291 


ward, both in America and in Europe—in America as 
far as Southern California. After the Glacial epoch, and 
the return of temperate conditions, they doubtless at- 
tempted to go northward again ; but these great changes 
were too much for them; they were wholly exterminated 
in Kurope, and nearly so in America. <A few were left 
stranded high up on the slopes of the Sierra Nevada, 
and on the cool, moist slopes of the Coast Ranges. ‘The 
species now in California are not identical with those 
found in the Miocene strata of Greenland; but the 
difference is only what we might expect after such ex- 
tensive migrations and such long and severe struggle 
for life. Further, it is noteworthy that the Miocene 
species fall into two groups, viz., the yew-like leaved 
and the cypress-like leaved. These are represented to- 
day in California, the one by the redwood, the other 
by the big-tree. ‘They are evidently direct descendants 
of the Miocene species, though somewhat modified. 

But it will be objected that there ought to be some 
cases of transitional forms showing transmutation—in 
fact, there ought to be some cases of species now form- 
ing under our eyes. There are, we believe, examples 
of such cases. But intermediate forms are not likely 
to be maintained long, especially if migrations occur 
to give rise to severe conflict of forms. In that case 
the intermediate forms are soon eliminated, and species 
become distinct. This important point will be dis- 
cussed more fully in the next chapter. 


CHAPTER IX. 


PROOFS FROM VARIATION OF ORGANIC FORMS, ARTI- 
FICIAL AND NATURAL. 


As already stated, page 40, the use of the method 
of experiment in the field of biology is, unfortunately, 
very limited. Nevertheless, it is already beginning to 
be used more and more in the department of physi- 
ology, and may be used also, to a limited extent, in 
the department of morphology. It is true that direct 
scientific experiments, for the express purpose of pro- 
ducing permanent modifications of form, and thus test- 
ing the theory of evolution, are of comparatively little 
value as yet, because the all-important element of time 
is wanting. The steps of evolution are so slow, and 
the time necessary to produce any sensible effect is usu- 
ally so great, that, In comparison, man’s individual 
lifetime is almost a yanishing quantity. But, from 
time immemorial, experiments have been wnconsciously 
made by man on domestic animals and food-plants, 
which bear directly on this subject. All domestic ani- 
mals and food-plants, and many ornamental flowering 
plants, have been subjected for ages to a process of 


PROOFS FROM VARIATION OF ORGANIC FORMS. 993 


artificial selection acting upon natural variation of off- 
spring. As wild species are modified, we believe, in- 
definitely by divergent variation and natural selection, 
so domestic species are modifiable certainly largely, 
perhaps indefinitely, by divergent variation and artif- 
cial selection by man. We all know the extraordinary 
modifications which have thus been gradually brought 
about in domestic animals, such as dogs, horses, sheep, 
pigeons, etc.; in food-plants, as cereal grains, garden- 
vegetables, etc., and in ornamental plants, as roses, 
dahlias, pinks, etc. We can only give very briefly the 
principles of the process by which these extreme modi- 
fications are produced, referring the reader to works 
specially devoted to this subject for more complete ac- 
counts. 

Let it be borne in mind, then (a), that inheritance 
is not only from the immediate parents, but from the 
whole line of ancestry. The inheritance from the im- 
mediate parents is, doubtless, usually greater than from 
any other one term of the ancestral series—the effect 
on the offspring of any previous generation becomes, 
doubtless, less and less as the distance from the off- 
spring increases—yet the swm of the ancestral inherit- 
ance is far greater than the immediate parental. Let 
it also be borne in mind (4) that true breeding from 


one form for many generations creates a fund of he- ~ 


redity in that form, and thus tends to produce fixity, 
rigidity, or permanence in that form. 
Now, the method of producing artificial breeds, some- 


994 EVIDENCES OF THE TRUTH OF EVOLUTION. 


times consciously, sometimes unconsciously, is, briefly, 
as follows: Suppose it be desired to obtain a variety 
of an animal, say a dog, having a certain character. 
We start from a common type, a (Fig. 68). If this type 





were allowed to breed naturally, the slight divergent 
variation of offspring represented by the radiating lines 
would neutralize one another by interbreeding, the indi- 
vidual differences would be ‘‘ pooled” in a common 
stock, and the species would remain substantially con- 
stant. But if among all these slightly divergent vari- 
eties we select one, b, which seems in the right direc- 
tion, and ruthlessly destroy all the others (indicated by 
crossing them out by the circular line), and breed this 
variety, 5, only, we shall get again a number of di- 
vergent varieties. It may be that the larger number 
of these will be backward, in the direction of the orig- 
inal type @, on account of the ancestral heredity in 
that direction, but some will again be in the desired 
direction. Let all the varieties other than the desired 
one, but especially the backward-going or reverting 
ones, be again destroyed, and the one kind only selected 
which seems to be in the right direction, viz., c. As 


PROOFS FROM VARIATION OF ORGANIC FORMS. 995 


we push the form thus from generation to generation 
in the desired direction, especially if we attempt to 
hasten too much the process, the resistance to move- 
ment—if I may use the expression—in that direction 
becomes greater and greater (shown by the decreasing 
distances between the successive points of divergence, 
a, b, c, d, etc.), and the tendency to reversion becomes 
stronger (shown by the greater number and length of 
the backward-going lines), until finally it is almost 
impossible to push any farther. We will suppose that 
x is such a limit. But if, now, we breed true on the 
point x, destroying the reversions or backward varia- 
tions for many generations, we will gradually accumu- 
late a fund of ancestral heredity on this point which 
increases with every added generation, until finally the 
tendency to reversion becomes small. The variety 
breeds true without further interference, or with only 
very general superintendence. Such a permanent va- 
riety is called a race. After a race is firmly established 
for a sufficient length of time, and the tendency to 
reversion is lost, it may itself become a new point of 
departure for the formation of new varieties or races, 
in the same or other directions. ‘Thus, during even the 
brief history of man, have been formed races of the 
different domestic animals, and useful and ornamental 
plants, differing so greatly from each other that, if found 
in the wild state, they would unhesitatingly be called 
different species, or even in some cases different genera, 
Now, if art can vary form so greatly, and in so 


i 
ee 


296 EVIDENCES OF THE TRUTH OF EVOLUTION. 


short time, why may not Nature in limitless time? If 
art by artificial selection, why not Nature by natural 
selection ? Nature is as rigid in selection and as ruth- 
less in destruction: why may we not expect similar or 
even much greater results? The process is similar in 
the two cases—i. e., selection among varieties in off- 
spring, only that the selection is natural instead of 
artificial, and the process is so slow that there is little 
tendency to reversion in the latter case. Suppose, 
then, we have a gradually changing physical environ- 
ment, or climate. Among the divergent varieties of 
any species in each generation, those would be pre- 
served which are most in accordance with the new 
climate, and the others would perish. This is natural 
selection, or survival of the fittest. Add to this the 
effect of the change in the organic environment. All 
species are modified by the changing physical environ- 
ment; but these modified species again all affect one 
another in the competitive struggle for life, and the 
strongest or swiftest, or most cunning, survive (natu- 
ral selection). Add to this, again, the struggle among 
the males for possession of the females—for reproductive 
opportunities—by which only the strongest and most 
courageous, or the most beautiful and attractive, leave 
progeny which inherit their peculiarities (sexual selec- 
tion). Add to these, finally, migrations, voluntary 
among higher and involuntary dispersals among lower 
animals and plants, and the consequent mingling of 
faunas and floras—the migrations subjecting them to 


PROOFS FROM VARIATION OF ORGANIO FORMS. 997 


great change of environment, both physical and or- 
ganic, and the mingling producing fiercer struggle for 
life—and we have in powerful operation many causes 
of modification. Add, I say, all these causes of modi- 
fication together, and then make the process slow and 
continuous through unlimited time, and where is the 
limit to the degree of change? Commencing in any 
species, from any point of departure, there are formed 
first slight modifications which would be called vari- 
eties ; then these modifications, continuing in the same 
direction, form races; these races by wider separation 
become species, and species in their turn become gen- 
era, etc. Comparing, again, to a growing tree, vari- 
eties are swelling buds; when they grow into twigs, 
they are species; when they branch again into different 
species, the branching stem becomes a genus, etc. 

We have thus far spoken only of the various forms 
of one factor, viz., the Darwinian factor of selection, 
whether natural or artificial. We have dwelt upon this 
one, because the natural and the artificial processes are 
so similar, and the artificial is so controllable. But there 
are other factors in operation, in art as well as in na- 
ture. We have already spoken (p. 73) of other factors 
of natural change. We have shown how changing 
physical environment affects function, and function 
affects form and_ structure, and how these slight 
changes are integrated by heredity through many gen- 
erations. We have also shown how wse or disuse in- 
creases or diminishes the size and change the form of 


998 EVIDENCES OF THE TRUTH OF EVOLUTION. 


parts, and these changes, also, however slight, are in- 
tegrated by heredity. 

Now, these factors are operative also in domestication 
of animals and cultivation of plants. No environment 
is so new and peculiar as domestication and cultivation. 
The soil and temperature in plants, food and housing of 
domesticated animals, tend to change form and structure 
of the offspring, although in a way which it is difficult 
intelligently to control, and thus are prolific of varieties 
from which to select. In fact, they often give rise to 
great and unexpected modifications, called sports, which 
form points of departure for new varieties and races. 
Now, in nature, not only are all these causes and factors 
of change in constant operation, but they act together in 
a peculiarly complex way. All the members of a fauna 
and flora, and the physical environment of any locality, 
constitute together a most complex and delicately ad- 
justed system of correlated parts. A change in one part 
is propagated through the whole system ; also, a change 
in one factor affects all other factors. When we add to 
this the large amount of time, in comparison with indi- 
vidual human life and observation, necessary to produce 
visible change of form, we can easily understand why the 
process is still imperfectly understood, although the fact 
is certain. 

But it will be asked, Are there, then, no differences 
between the artificially made extreme varieties equiva- 
lent, so far as difference of form is concerned, to species, 
and real natural species ? There are. If there were not, 


PROOFS FROM VARIATION OF ORGANIC FORMS. 299 


there would never have been any doubt about the deriva- 
tive origin of natural species. But if it be asked, Are 
not these differences fundamental, and therefore fatal to 
the argument for evolution derived from this source ? 
we answer, we think not. We will deal frankly and 
fairly with these differences. 

First Difference, Reversion.— The strong tendency 
of artificial varieties to reversion, even during the process 
of formation, and especially their complete reversion to 
the original type if the hand of man be withdrawn—i. e., 
if left to themselves, or become wild—is supposed to show 
an essential difference between such varieties, however 
extreme, and true species—is supposed, in fact, to prove 
an indestructible permanency of specific types. Nature 
disowns these artificial forms, and as it were brands them 
with bastardy. Not only so, she strives ever to destroy 
them. The supporting hand of man is necessary to 
sustain them. Left to themselves and to Nature, they 
quickly revert to the original type. If all the extreme 
varieties of dogs, from the greyhound and Newfoundland, 
on the one hand, to the terrier and lap-dog on the other, 
were turned loose on an isolated island, uninhabited by 
man but full of other animals, and left there to shift for 
themselves—and the island were visited again after a 
lapse of a hundred or a thousand years—it is probable 
that a uniform species, something like to, though per- 
haps not identical with, the wolf, would be found. They 
would have reverted to the original or nearly the origi- 
nal wild type from which they were produced by domes- 


930 EVIDENCES OF THE TRUTH OF EVOLUTION. 


tication. All or nearly all that was done by man would 
have been undone by Nature. This reversion is one test 
of species. | 

But the reason of this tendency to reversion is ob- 
vious: First, the time was too short, the rate of change 
was too rapid, in the artificial formation of these varieties. 
There was not time enough to accumulate a fund of he- 
redity on each successive stage of the change. Therefore 
the form is unstable and the tendency to revert is strong. 
Compare the fleeting days and the hurrying impatience 
of man with the infinite time and the divine patience of 
Nature! But mere instability is not the principal cause 
of reversion. Secondly, in the case of artificial forms in 
a wild state, natural selection compels reversion. Every 
species in a wild state must of course be in harmony with 
the environment. But artificially made forms are in 
harmony with the artificial environment of domestica- 
tion, but not with the environment of nature. In nature 
the fittest survive, but artificial breeds are not fit to sur- 
vive in a state of nature. They are therefore quickly 
destroyed in the struggle for life, or must be modified. 
Nature immediately begins to select the fittest, and 
gradually in the course of time produces one or more 
uniform species, similar to that from which they came, 
or perhaps to what they would have been by this time if 
left to the operation of natural causes under the condi- 
tions supposed. But natural species, if they are formed, 
as the derivationists suppose, by the operation of natural 
causes, can not revert unless the conditions revert ; for 


PROOFS FROM VARIATION OF ORGANIC FORMS. 931 


the same causes which operated to produce, still con- 
tinue to operate to keep, the species. Take an example: 
The form, the habits, and the instincts of the pointer 
have been made by a slow process of artificial selec- 
tion of divergent varieties of offspring, and by training of 
individuals continued and its effects accumulated through 
‘many generations. But this form and these habits and 
instincts, so laboriously produced, would be quickly de- 
stroyed by Nature. ‘The pointer, Icft to himself, must 
either change or become extinct, because not adapted 
to the wild state. Such instincts and habits would 
not only be of no use, but would be incompatible with 
success in the struggle for life. But suppose for a mo- 
ment that these habits and instincts were useful to 
the animal in a wild state; evidently they would be in- 
stantly seized upon by natural selection, and not only 
perpetuated but intensified until a very distinct species 
would be produced. ‘The same is true of all other races 
of dogs. If the Newfoundland, the greyhound, and the 
pug were all turned loose in a forest, and if each of these 
kinds were admirably adapted to some place in the econ- 
omy of Nature—for some special mode of food-getting 
without corresponding disabilities in other directions (as 
must be the case if made by natural selection)—there can 
be no doubt they would each survive, and their charac- 
ters intensified ; intermediate forms would disappear (for 
reasons which we shall see presently), and we would soon 
have three distinct species, or perhaps we would even 
call them distinct genera. 


932 EVIDENCES OF THE TRUTH OF EVOLUTION. 


Second Difference, Intermediate Forms.—Natural spe- 
cies are distinct—marked out with hard and fast lines— 
while artificially-made races, even though in their typical 
forms they differ as much or more than natural species, 
shade into one another by insensible gradations. Jn an- 
swer and explanation of this difference we remark: If 
species or modified forms of any kind, whether natural 
or artificial, are made by natural causes, and not at once 
out of hand by supernatural creation, then of course 
there must have been gradations in the process of mak- 
ing. Now, in the artificial case, the whole process as 
well as the result lies within the limits of observation, 
while in the natural case only the final result. But it 
will be asked, Why are the gradations not seen also in 
the final result? We answer, because the intermediate 
forms are eliminated in the struggle for hfe, and not re- 
produced by cross-breeding. If artificial races always 
bred true—i. e., without crossing, as natural species do— 
they would probably soon be as sharply demarked. Cross- 
breeding is the great cause of the shadings between do- 
mestic races. This brings me to the third and most im- 
portant difference. 

Third Difference, Cross-Fertility. __ Artificially saan 
races breed freely and without repugnance with one an- 
other, and the offspring of such cross-breeding is in- 
definitely fertile. Natural species will not usually unite 
with one another, being prevented by sexual repugnance 
and other causes. Or, if they do sexually unite, there 
is either no offspring, or else the offspring is sterile, 


PROOFS FROM VARIATION OF ORGANIC FORMS. 933 


and therefore the intermediate form dies out in the 
first generation; or else the offspring is imperfectly 
fertile, and therefore the intermediate form is elimi- 
nated in a few generations, and the species remain 
distinct ; or else the offspring is more fertile with the 
parent stocks, and therefore revert to the parent stocks, 
and still the species remain distinct. Such infertile, or 
imperfectly fertile, offspring—the result of crossing of 
species—are called hybrids. 

This is regarded as a most important test of true 
species, as contrasted with varieties or races. There 
are two bases on which species may be founded. Spe- 
cies may be based on form, morphological species ; or 
they may be based on reproductive functions, physio- 
logical species. By the one method a certain amount 
of difference of form, structure, and habit, constitutes 
species ; according to the other, if the two kinds breed 
freely with each other and the offspring is indefinitely 
fertile, the kinds are called varieties, but if they do 
not they are called species. The two tests, however, 
do-not always accord. Every now and then we find 
undoubted morphological species which may be crossed 
and produce indefinitely fertile offspring. Yet it is 
certainly true that species are usually cross-sterile, while 
varieties, whether natural or artificial, are cross-fertile. 

In explanation of this important difference, let it 
be observed that there are here two things which must 
be kept distinct in the mind, although they are, doubt- 
less, closely allied—viz,, sexual repugnance (psychologi- 


234 EVIDENCES OF THE TRUTH OF EVOLUTION. 


cal element) and cross-sterility (physiological element). 
The former is found, of course, only in the higher 
animals, where fertilization is voluntary. The latter is 
universal among all living things. This latter, there- 
fore, is the more fundamental and essential element, 
and the former may be regarded as its psychical sign 
in the higher animals. It is of this latter, therefore— 
i, e., cross-sterility—that we shall speak mainly. 
Suppose, then, we have growing together in the same 
locality many species of pines or oaks, or other ane- 
mophilous trees. The whole air is filled with the pollen 
of many species, and every germ-cell must receive many 
kinds of male cells, and yet there are no hybrids, but, 
on the contrary, the species remain distinct. So also 
in case of hermaphrodite animals, where the fertilization 
is involuntary ; many aquatic species are found together 
in the same locality, and the water is filled with sperm- 
cells of many different species. Many kinds of sperm- 
cells must fall on each germ-cell, and yet there are no 
hybrids; the species remain distinct. In all such cases 
we must suppose that there is, among the different kinds 
of male cells, a struggle for the possession of the germ 
or female cell, or a sort of sexual selection by the female 
cell among the competing male cells, and the fittest— 
the most in accord; i. e., those of the same species 
—prevail. This is universal. But in the higher ani- 
mals, in addition to. the prepotency of male cells of the 
same species, and comparative infertility in case of union 
of those of different species, sexual attraction and sexual 


PROOFS FROM VARIATION OF ORGANIC FORMS. 235 


repugnance contribute to the same result, and species 
are thus doubly separated. ‘Thus sexual selection is of 
two kinds: selection of individuals for union (psychical), 
and selection of sperm-cells for fertilization (physiologi- 
cal). The one kind is usually the sign of the other— 
attraction the sign of fertility, and repugnance of sterility. 

But in the domestic state it is all otherwise. Free 
competition between individuals or between cells is not 
allowed. Thus, for example, among plants, crossings 
may be forced and hybrids made in gardens which would 
never occur in Nature. The florist prevents fertilization 
in the same kind and compels fertilization of a different 
kind. If male cells of the same kind were allowed to 
compete, the result would be different. Doubtless the 
same method would succeed in many lower animals. 
So also in higher animals free competition and sexual 
selection for union are often not allowed, and therefore 
animals of different species, such as the horse and the 
ass, unite, which would not do so if they were free to 
select as in the wild state. These two are widely dis- 
tinct species, sometimes even called genera, and there- 
fore the offspring is infertile; but two closely allied 
species, such as two species of wolf, or of the fox, in a 
domestic state would probably not only unite but pro- 
duce indefinitely fertile offspring. In fact, it is almost 
certain that the dog was made by a mixture of several 
species of wolf, most, perhaps all, of them now extinct.* 

* “Origin of Races of the Dog.” “ Annals and Magazine of Natural 


History,” vol. xvii, p. 295. 1886. 
17 


936 EVIDENCES OF THE TRUTH OF EVOLUTION. 


On the other hand, it is not at all certain that the 
extreme varieties of dogs have not passed the limit of 
greatest attraction, and therefore of greatest cross-fer- 
tility, and that, if allowed free choice, as in Nature, 
they would not breed true, or tend to breed true, with 
their own kind, and intermediate kinds die out in the 
struggle for life. 

Law of Cross-breeding.—Before going any further in 
this discussion, it is necessary to bring out another 
point of extreme importance in the formation of vari- 
eties, both natural and artificial—a point which I be- 
lieve throws light upon the very significance of sex 
itself—I refer to the effect of cross-breeding. 

It is a curious and most significant fact that dif- 
ferent varieties, both natural and artificial, are, up to 
a certain limit, not only cross-fertile and cross-attract- 
ive, but even more so than individuals of the same 
variety. Long experience has shown that very close | 
breeding of the same variety for a long time fixes the 
kind but weakens the stock, especially in fertility, while 
judicious crossing of varieties strengthens the stock, 
increasing its fertility, and especially producing plas- 
ticity or variability. Therefore breeders, if they wish 
to preserve a valuable variety, breed close; but, if they 
wish to make new varieties, cross-breed. But we have 
already seen that species are usually cross-sterile. 'There- 
fore there must be some regular law of increase to a 
maximum, and again decrease to zero. It is this law 
that I now wish to investigate. 


PROOFS FROM VARIATION OF ORGANIC FORMS. 237 


In the lowest animals and plants multiplication of 
individuals and the continuance of the kind are inde- 
pendent of sex, and therefore in such there may be no 
sex at all. The sexual elements are not yet differen- 
tiated. An individual divides itself into two; each 
grows to the original size and again divides into two, 
and so on, it may be indefinitely. In this lowest form 
of reproduction the individual is sacrificed to the kind, 
or else we may regard the kind as an extension of the 
individual, and reproduction as a modification of growth. 
But there are other sexless modes of reproduction, found 
in nearly all plants and many lower animals, in which 
the individuality is not sacrificed. The next step in 
the ascending scale is reproduction by budding. In 
this case a bud is formed which grows into a perfect 
individual, and may remain attached to the parent 
stalk, forming together a compound individual, as in 
most plants and many lower animals, such as the coral; 
or it may separate and assume independent life, as in 
some plants and many lower animals. Im still other 
animals, as in many hydrozoa, the budding function is 
relegated to a special part, which thus becomes a re- 
productive organ. ‘The next step is the placing of the 
budding organ, for greater safety, in an interior cavity. 
This is the case with aphids. Now, why would not 
this be an excellent mode of reproduction for all ani- 
mals, man included ? Why was sex introduced at all? 
There are very sufficient reasons, of many kinds, which 
may come up later; but the fundamental reason, in 


938 EVIDENCES OF THE TRUTH OF EVOLUTION, 


connection with evolution, is the funding of individual 
differences tn a common offspring, thereby giving to the 
offspring a tendency to divergent variation. 

Now, on-sexual reproduction is absolute true breed- 
ing. The law of like producing like is absolute. He- 
redity is all-powerful, and tendency to variation is nil. 
These modes of reproduction are in fact but a modifica- 
tion of growth and an extension of the individual. Evo- 
lution-changes in animals produced in this way only 
must be very slow, since the most powerful factor of 
evolution, viz., natural selection among divergent varie- 
ties of offspring, would be wanting. In the earliest times, 
therefore, before sex was yet declared, we may imagine 
that physical environment was the great and only factor 
of change. Sexual reproduction introduces the new ele- 
ment of variation of offspring from which Nature makes 
her selections ; and this element of variation is appar- 
ently the result of the union of diverse individuals, and 
the funding of these differences in a common offspring, 
and thus a double inheritance of individual character- 
istics from the parents and a multiple inheritance of the 
same from the ancestry. See, then, with this end in view, 
the pains Nature has taken to make the difference be- 
tween the uniting individuals and the diversity of inher- 
itance by the offspring as great as possible, and yet the 
gradual way in which she has accomplished it. As al- 
ready said, the lowest form of reproduction is that by 
fission. Next comes budding in any part indifferently. 
Next comes the relegation of the budding function to a 


PROOFS FROM VARIATION OF ORGANIC FORMS. 239 


particular part. This is the first appearance of a repro- 
ductive organ. Next comes the placing of this organ, 
for greater safety, within. Thus far all is non-sexual 
reproduction—all a modification of growth—an extension 
of the individual, like the propagation of plants by cut- 
tings and by buds. Then comes sexual reproduction in 
its lowest forms. 

It may be well to stop here, to show the entire differ- 
ence between this and non-sexual modes. ‘The latter, we 
have seen, is only a modification of growth, an extension 
of the individual. Now, sexual reproduction is the op- 
posite of all this. Growth is a constant multiplication 
of cells. One cell is ever becoming two similar cells—or, 
if we call them individuals, one individual is ever becom- 
ing two similar individuals. But in sexual reproduction 
we have an exactly reverse process. Reduced to its sim- 
plest terms, sexual reproduction is the fusion of two di- 
verse cells, sperm-cell and the germ-cell, to form one cell, 
the ovule—literally, a diverse twain forming one flesh. 
In its higher forms it is the union of diverse individuals 
to bring about the same result. Instead of one cell be- 
coming two, it is two cells becoming one ; instead of one 
individual becoming two in the offspring, it is two indi- 
viduals becoming one in the offspring. But this great 
change was not brought about at once, but only in the 
most gradual manner. First, the sexual elements—sperm- 
cell and germ-cell—are separated, but in the same organ. 
Then the organs—spermary and ovary—are separated, 
but in the same individual. This is the condition of self- 


240 EVIDENCES OF THE TRUTH OF EVOLUTION. 


fertilizing hermaphroditism so common among plants 
and lower animals. Then comes cross-fertilizing her- 
maphroditism ; and Nature takes much pains and uses 
many ingenious devices to prevent self-fertilization and 
insure cross-fertilization. Now, for the first time, we 
have slight individual differences funded in a common 
offspring. Then, in order to absolutely forbid self-fertili- 
zation, and at the same time allow greater differences in 
the crossing individuals than could be attained in her- 
maphroditic individuals, the sex organs are separated in 
different individuals, and fertilization can only take 
place by voluntary union. 'Then, to insure the union of 
suitable individuals, and forbid the ban between unsuit- 
able, there are introduced sexual attraction and repulsion. 
Then, last of all, the difference between the two sex- 
individuals becomes greater and greater as we goup. It 
is conspicuous only in vertebrates and some insects, and 
very conspicuous only in birds and mammals. 

We see, then, as we go up the taxonomic, and undoubt- 
edly also the phylogenic series, that there is a cross- 
breeding of more and more diverse individuals, a funding 
of more and more divergent characteristics in a common 
offspring. Why is this? I answer, for the sake of Jdet- 
ter results in the offspring. This is abundantly shown . 
by direct experiment. In hermaphroditic plants in which 
there may be either self-fertilization or else cross-fertiliza- 
tion with other individuals of the same species, the latter 
produces better results in number and vigor of offspring. 
But there are other advantages, more difficult to prove 


PROOFS FROM VARIATION OF ORGANIC FORMS. 241 


but none the less certain, and of the greatest importance 
in evolution : First, as already stated, complexity of in- 
heritance, like complexity of composition in a chemical 
substance, gives instability to the embryo, and thus lia- 
bility to variation in the offspring ; and this in its turn 
furnishes the material for selection of the fittest. Again, 
it seems to me that there is a direct tendency to improve 
the offspring by a sort of struggle in the embryo among 
the various qualities inherited from both sides, and a 
survival of the best and strongest—a sort of pre-potency 
of strong qualities. 

Can divergence of uniting individuals and the fund- 
ing of diverse characteristics go any further? It may. 
The differences of the uniting individual may be still fur- 
ther increased, and the resulting offspring still further 
improved by the cross-breeding of different varieties of 
the same species, for we thus add varictal differences to 
sexual differences in the uniting individuals. It is well 
known that too close breeding, or consanguineous breed- 
ing, or breeding in and in, as it is variously called, if 
continued long, has a bad effect on the offspring, weaken- 
ing the stock, while judicious crossing of varieties within 
certain limits of difference has a good effect, strengthen- 
ing the stock and increasing its fertility. It probably 
does so in two ways : one direct, by funding many diverse 
qualities from both sides, and the survival in the off- 
spring of the strengest and best ; the other indirect, by 
giving plasticity, instability to the embryo, and varia- 
bility to the offspring, and therefore abundant material 


2949 EVIDENCES OF THE TRUTH OF EVOLUTION. 


for the operation of selection, either by man or by Na- 
ture. We said, ‘‘ within certain limits of difference.” If 
the difference is extreme, as in extreme varieties and 
races, then the effect becomes again bad, and more and 
more so as the limit of specific difference is approached ; 
at which limit at last Nature shuts down and forbids the 
bans. Thus, then, there is in cross-breeding a regular law © 
of effect, increasing to a maximum and again decreasing, 
which may be graphically represented by a curve (Fig. 
69). In this figure the horizontal line represents the or- 





Fia. 69. 


dinary level of the type ; distances on this line represent 
differences, individual, varietal, or specific ; ordinates 
above or below represent the effect, good or bad, of cross- 
ing. Thus ss’ represent two species, and the line between 
represents their specific differences; 7 7’ represent different 
races or permanent varieties ; vv’ two strong varieties ; 
dd’ ordinary individual differences ; ¢ c’ close resembling 
or consanguineous individuals. The undulating line rep- 
resents the effect of crossing these various kinds. It is 
seen that ‘‘in-and-in breeding,” ¢c’, produces bad effect 
(negative ordinates) ; breeding of ordinary individual 
differences, dd’, keeps the stock at the ordinary level—in 
its typical form ; crossing two strong varieties, vv’, pro- 
duces maximum good effect (positive ordinates) ; crossing 


PROOFS FROM VARIATION OF ORGANIC FORMS. 943 


decided races produces again bad effects, which become 
infinitely bad as we approach species, s $’.* 

It is generally admitted that long-continued very close 
breeding has a bad effect. Even in plants, Darwin has 


shown that cross-fertilization has better effect than sclf- - 


fertilization, this last being of course the closest possible 
breeding. But it is probable that the principal bad effect 
is not on the stock but on the process of evolution. Very 
close breeding weakens the stock, ordinary breeding of 
individual differences maintains the stock at the or- 
dinary level and fixes it. Cross-breeding of varieties 
strengthens the stock, and also (and this is its main 
advantage) produces plasticity in the stock, gives rise to 
strong divergent. variations, or even sports, and thus be- 
comes a main agent in evolution. It is probable, more- 
over, that the higher the function the more sensitive is it 
to these effects of breeding. Therefore, the effect is great- 
er in man than in any other animal. It is true that many 
have doubted the bad effect of close breeding in man, 
and have brought forward formidable statistics to substan- 
tiate their position ; but these doubtless take no account 
of the most important function, the psychic, and espe- 
cially the most important element in every function, so 
far as evolution or progress Is concerned, viz., plasticity 
or capability of progressive improvement. The tendency 
of consanguineous breeding, or even the breeding of per- 


* Mr. Galton (“ Nature,” August 26, 1886) has used a diagram simi- 
lar to the above (which I first used in 1879) to illustrate the law of 
sexual attraction and repugnance. 


944 EVIDENCES OF THE TRUTH OF EVOLUTION. 


sons of like character and experiences, as in an isolated 
community, is, if not to deteriorate the physique, at least 
to fix, stereotype the character, and thus to check social 
progress. Contrarily, the crossing of varieties of the 
same race seems not only to strengthen but, by the diverse 
inheritance, to produce plasticity of character and ca- 
pacity for progress. But the difference between the pri- 
mary races seems too great for crossing with advantage. 
Some degree of sexual repugnance which undoubtedly 
exists between the primary races is the psychical sign of 
this fact.* 

If, now, we go back to what we said before taking up 
this subject of the effect of cross-breeding, we at once see 
that there is an apparent flaw in all our reasonings. If 
close in-and-in breeding produced better and more nu- 
merous offspring than cross-breeding between slight va- 
rieties, then, indeed, such varieties would be preserved, 
and increase in divergence from generation to genera- 
tion until they became species. Or, in any case, if, in 
any way, divergence could reach the. point of extreme 
varieties or races, or what are called sub-species, then 
commencing cross-sterility would complete the separa- 
tion, and thus form true species. But how can the pro- 
cess of progressive divergence begin, when slight varie- 
ties are even more fertile by cross-breeding than by close 
breeding ? Is it not evident that, with every generation, 


* This subject is more fully discussed by the author in an article en- 
titled “ Genesis of Sex,” in “‘ The Popular Science Monthly,” vol. xvi, p. 
167, 1879. 


PROOFS FROM VARIATION OF ORGANIC FORMS. 945 


the slight varieties would cross-breed with one another 
and with the parent stock, and thus all varietal differ- 
ences would be funded into a common stock, and the 
type would be preserved unchanged ? This, as already 
pointed out (p. 76), has always been the chief difficulty 
in the way of imagining how varieties can grow into spe- 
cies ; and the difficulty is only increased by our discus- 
sion of the law of cross-breeding. Now, just here, Dr. 
Romanes’s most important and prolific idea comes to our 
help, and, as it seems to us, completely solves the diffi- 
culty. 

Accordiag to Dr. Romanes, no organ is so subject 
to variation as the reproductive, and this in no respect 
so much as in degrees and kinds of fertility—we might 
almost say so subject to freaks of cross-sterility. Now, 
suppose we start with any well-defined species in a state 
of nature. With every generation there are many 
shghtly divergent individual varieties, some greater and 
some less; but these are all immediately swamped by 
crossing with one another and with the parent stock, 
and the species remains unchanged. But suppose among 
these divergent variations there arise, from time to 
time, some which affect the reproductive organs in such 
wise that the variety, though perfectly fertile with its 
own kind, is infertile, or imperfectly fertile, with other 
varieties, and especially with the parent stock. The 
change may be only in the ¢ime of flowering in plants, 
or season of heat in animals, or it may be actual in- 
fertility in sexual union. Right here we have the be- 


946 EVIDENCES OF THE TRUTH OF EVOLUTION. 


ginning of a new species. The variety is sexually iso- 
lated from the parent stock by cross-sterility, and 
therefore all its peculiarities, however trivial, are pre- 
served by true breeding. Cross-breeding is necessary to 
make species, but true breeding preserves them. Cross- 
breeding tends ever to make varieties, but immediately 
destroys them again. This constant forming and swamp- 
ing, separating and again merging of varieties, like 
mixing of dough, makes the whole mass (stock) more 
and more plastic and subject to variety. This plas- 
ticity finally gives rise to varieties of the kind which 
produces species by sexual isolation. By continued 
merging the centrifugal forces continually increase, but 
are continually repressed by crossing, until finally vari- 
eties break away to form species. 

Now it is easy to see, from this point of view, why 
artificial varieties are cross-fertile. It is because in 
artificial breeding we are intent only on making vari- 
eties in form, size, color, etc., and not at all on making 
any characterized by cross-sterility with the parent 
stock. Oross-sterility with the parent stock, or with 
other varieties, would be of no advantage, because we 
control the breeding, and can breed true if we desire. 
Sexual isolation is not necessary, because we can use 
physical isolation. On the contrary, such cross-sterility 
would be a positive disadvantage to the breeder, by 
limiting the range of his experiments just where they 
would be most prolific in making new varieties. Hence, 
as might be expected, all domestic varieties are cross- 


PROOFS FROM VARIATION OF ORGANIC FORMS. 247 


fertile, unless it be the extreme varieties, which may, 
in some instances, have passed the limit of greatest 
fertility. 

If this idea be true, then species which have origi- 
nated in the same locality ought to be always cross- 
sterile, but species which have grown up apart, in widely 
separated geographical regions, ought to be sometimes 
cross-fertile, because they were isolated by physical not 
by sexual barriers. Such, Dr. Romanes thinks, is a fact. 
It is, however, a very important point, which ought to 
be carefully investigated. We say ‘‘sometimes.” It is 
probable that most geographical species also are cross- 
sterile; for, although the isolation by cross-sterility of 
slight varieties be the main cause of the origin of species, 
yet a species formed by isolation of any other kind 
will gradually become cross-sterile with other species. 
Although cross-sterility be the main cause of divergence, 
yet divergence beyond a certain limit, however caused, 
will bring about cross-sterility, because the reproductive 
organs will partake of the general change going on in 
every part. 

Application.—Suppose, then, a species breeding natu- 
rally in a wild state. Individual varieties are constantly 
being formed and again funded back into the common 
stock by cross-breeding. If the varieties thus formed 
be decided, the cross-breeding will strengthen the stock, 
and especially will preserve and increase its plasticity or 
tendency to variation. Finally, among the widely di- 
vergent varieties there is one affecting the reproductive 


248 EVIDENCES OF THE TRUTH OF EVOLUTION. 


organs of several individuals in such wise that they are 
infertile, or imperfectly fertile, with the parent stock, 
though perfectly fertile among themselves. ‘These form 
a new species, which continue to increase indefinitely. 
Objection answered.—This view completes the answer 
to an objection which is often made to evolution: “ If 
natural species are formed by transmutation, why is it 
we do not find intermediate links? Why is not organic 
nature made up only of individual forms, shading in- 
sensibly into each other in such wise that classification 
becomes a mere device to handle more conveniently 
complex material? Why is it that groups, especially 
species, are marked out with hard and fast lines ?” 
We have heretofore answered this by saying that inter- 
mediate forms are eliminated. So they are, but how? 
Dr. Romanes’s idea of physiological selection largely 
answers this. It is by the funding of ordinary varie- 
ties into a common parental stock by crossing, and 
separating specific varieties by cross-sterility. Thus the 
organic field is broken up into points about which 
variations oscillate. As every mass of matter, when 
closely examined, is found to consist of aggregations 
about centers of cohesive attraction as discrete granules 
or crystals, and only exceptionally do we find a homo- 
geneous vitreous structure; even so organic forms ag- 
gregate about points of sexwal attraction, and the whole 
mass consists of discrete species, and only exceptionally 
—i. e., in domestication—do we find insensible shad- 
ings. Now, species are the smallest aggregate of indi- 


PROOFS FROM VARIATION OF ORGANIC FORMS. 249 


viduals, as granules are of molecules. Species are more 
distinctly marked out by hard and fast lines than are 
other taxonomic groups only because they are the last, 
going downward, that are cross-sterile—because right 
here is the change from cross-sterility to cross-fertility. 

If this view be true, then in ¢he same locality spe- 
cies ought to be always distinct and without shadings. 
If we find shadings at all, it ought to be in interme- 
diate geographical regions, where isolation is not sexual 
but physical. Now, this is exactly what we find to be 
the fact. Innumerable examples of such intermediate 
forms in intermediate geographical regions are now 
known, especially among birds and reptiles, and exam- 
ples have so increased in modern times, by closer study, 
that naturalists, especially ornithologists, have been com- 
pelled to resort to a trinomial nomenclature in order 
to designate these geographical sub-species.* 

If any further explanation is necessary, it will prob- 
ably be found in the following suggestions : 

1. The number of individual varieties constantly 
being formed is almost infinite, but the number of 
places in nature is very limited. Now, among the in- 
finite number of slight individual varieties formed with 
every generation, the competitive struggle will be se- 
verest between those most nearly alike, because they are 
competitors for the same place. Only one kind suc- 


* For examples of this the reader is referred to Cope, “ Bulletin of 
the National Museum,” No, 1; and to Coues’s “‘ Key to North American 
Birds,” last edition. 


2950 EVIDENCES OF THE TRUTH OF EVOLUTION. 


ceeds, viz., the fittest. Intermediate forms are, there- 
fore, exactly those which are eliminated in the most 
wholesale way. 2. Add to this the fact that, as soon 
as divergence, from whatsoever cause, reaches a certain 
point, sexual repugnance or cross-sterility, or both, come 
in to perpetuate and increase the separation already 
commenced. 3. Add to this, again, that migrations in 
higher animals, and involuntary dispersals in lower ani- 
mals and in plants, and the mingling together of dif- 
ferent faunas and floras, produces a still fiercer struggle 
for life, especially between natives and invaders, and 
thus great numbers of forms are destroyed ; all but the 
fittest are weeded out, and therefore the distinctness of 
the remainder is greatly increased. Periods of great 
changes of physical geography and of climate, and there- 
fore of wide and general migrations, are also periods 
of great weedings-out of unfit forms. Thus it happens 
that existing faunas and floras are little else than iso- 
lated remnants. 

To illustrate, again, by a growing tree: If all the 
buds of a tree lived and grew, they would soon become 
so numerous that they would together form a solid 
hemispherical mass, like a coral-head, with no room 
between for leaf or light or air. But ninety-nine one- 
hundredths of buds die in the struggle for light and 
air, and therefore the survivors are distinct growing 
points, widely separated from each other. Species are 
such extreme, but separated, twiglets of the tree of life. 

Objection—But it will be objected, again: The twig- 


PROOFS FROM VARIATION OF ORGANIC FORMS. 951 


points are, indeed, separate, but the twigs themselves 
must meet somewhere lower down, where they began 
to grow. Intermediate links may be wanting now, but 
they must, of course, have existed once—i. e., in pre- 
vious geological times, and therefore ought to be found 
fossil. In distribution in space or geographically, organic 
kinds may be marked off by hard-and-fast lines, but, 
if their derivative origin be true, in their distribution 
in time or geologically, there ought to be many examples 
of insensible shadings between them. In fact, if we 
only had all the extinct forms, the organic kingdom, 
taken as a whole and throughout all time, ought to 
consist not of species at all, but simply of individual 
forms, shading insensibly into each other, like the colors 
of the spectrum, and our classification ought to be a mere 
matter of convenience, having no counterpart in nature. 
But this is not the fact. On the contrary, the law of 
distribution in time is apparently similar in this respect 
to the law of distribution in space, already given (page 
169). Asin the case of contiguous geographical faunas, 
the change is apparently by substitution of one species 
for another, and not by transmutation of one species 
into another. So also in successive geological faunas, 
the change seems rather by substitution than by trans- 
mutation. In both cases species seem to come in sud- 
denly, with all their specific characters perfect, remain 
substantially unchanged as long as they last, and then 
die out and are replaced by others. Certainly this 


looks much like immutability of specific forms, and 
18 


952 EVIDENCES OF THE TRUTH OF EVOLUTION. 


supernaturalism of specific origin. We have, we be- 
lieve, satisfactorily explained this in the case of geo- 
graphical distribution (page 201), but how can we ex- 
plain it in the case of geological distribution ? 

Answer.—1. The reason for this, given by Darwin 
and other evolutionists, is the extremely fragmentary 
character of the geological record. If the existing 
faunas and floras are but isolated remnants, the rest 
having been destroyed by migrations and conflicts, how 
much more are fossil faunas and floras but fragmentary 
remnants, the rest having been Jost, partly because never 
preserved, and partly by destruction of the record! If 
from this cause existing species are widely separated, 
how much more ought we to expect to find fossil species 
distinct and widely separated ! 

This is undoubtedly in most cases a true and suffi- 
cient answer, yet we think, the fragmentariness of the 
geological record has been overstated. While it is true 
that there are many and wide gaps in the record; while 
it is true, also, that even where the record is continuous 
many forms may not have been preserved, yet there are 
some cases, especially in the Tertiary fresh-water de- 
posits, where the record is not only continuous for hun- 
dreds of feet in thickness, but the abundance of life 
was very great, and the conditions necessary for preser- 
vation exceptionally good. In such cases the number 
of fossil species found on each horizon seems to be as 
great as in existing faunas over equal space. The rec- 
ord in these cases seems to be continuous and without 


PROOFS FROM VARIATION OF ORGANIC FORMS. 253 


break, and crowded with fossil forms ; and yet, although 
the species change greatly, and perhaps many times, in 
passing from the lowest to the highest strata, we do 
not usually, it must be acknowledged, find the gradual 
transitions we would naturally expect, if the change 
were effected by gradual transformations. The incom- 
pleteness of the record, therefore, although a true and 
important cause, is not the whole cause. 

In further and completer answer to this greatest of 
all objections, we will throw out the following sug- 
gestions : 

2. We must remember that considerable latitude is 
allowed by the anti-derivationists to variation of species ; 
so much so, indeed, that it is often difficult to draw the 
line between well-marked varieties and closely-allied spe- 
cies. Now, according to the derivationist, these strong 
varieties, breeding usually true, are naught else than 
commencing species. 

3. On every side and everywhere, both in existing 
faunas and in fossil forms, but especially in the latter, 
we find innumerable examples of transitions, or inter- 
mediate forms, between all the higher groups, such as 
genera, families, orders, and classes. It is, n fact, by 
means of these that the great law of differentiation 
from generalized types has been established. It is, 
therefore, only between species that such intermediate 
forms are rare. 

4, But even between species such intermediate forms, 
though rare, have been pointed out, both in existing 


254. EVIDENCES OF THE TRUTH OF EVOLUTION. 


and in extinct faunas. But the opposition contend that, 
in all such cases, the previously supposed species are 
only varieties. We have already (page 61) spoken of 
the obvious fallacy involved in this position. Species 
are first defined as forms distinct and without inter- 
mediate links, and then we are challenged to find such 
links; and when, with much labor, we find them, they 
say the supposed species are not species, but only vari- 
eties. But there are some cases in which this subterfuge 
will not do. There are cases in which the transitions 
are between forms so extreme that they can not, by any 
stretch of the term, be called varieties. We will select 
and dwell upon but one striking example, viz., the fossil 
forms of the Tertiary fresh-water deposits of Steinheim. 

In Wiirtemberg, near the little village of Steinheim, 
are found certain strata of sand and lime, which are evi- 
dently deposits from a small lake of Tertiary times. The 
deposits are extremely rich in fossil shells, especially of 
the different species of the genus Planorbis. As the de- 
posits seem to have been continuous for ages, and the 
fossil shells very abundant, this seemed to be an excel- 
lent opportunity to test the theory of derivation. With 
this end in view, they have been made the subject of ex- 
haustive study by Hilgendorf in 1866,* and by Hyatt in 
1880.+ In passing from the lowest to the highest strata 


* “ Monatsbericht d. k, Preuss. Akademie d. Wissenschaft zu Berlin,” 
for July, 1866. 

+ “Genesis of Tertiary Species of Planorbis at Steinheim.” A. Hyatt, 
Anniversary Memoir of the Boston Society of Natural History, 1880. 


PROOFS FROM VARIATION OF ORGANIC FORMS. 955 


the species change greatly and many times, the extreme 
forms being so different that were it not for the inter- 
mediate forms they would be called not only different 
species but different genera. And yet the gradations are 
so insensible that the whole series is nothing less than a 
demonstration, in this case at least, of origin of species 
by derivation with modifications. The accompanying 
plate of successive forms (Fig. 70), which we take from 
Prof. Hyatt’s admirable memoir, will show this better 
than any mere verbal explanation. It will be observed 
that, commencing with four slight varieties—probably 
sexually isolated varieties —of one species, each series 
shows a gradual transformation as we go upward in the 
strata—l. e., onward in time. Series I branches into 
three sub-series, in two of which the change of form is 
extreme. Series IV is remarkable for great increase in 
size as well as change in form. In the plate we give only 
selected stages, but in the fuller plates of the memoir, 
and still more in the shells themselves, the subtilest gra- 
dations are found. 

This case is striking, partly because it is a very favor- 
able one, but mainly because it has been so carefully 
studied. ‘There can be no doubt that equally careful 
study would reveal the same transition in many other 
cases. Nor are such transitions confined to the lower 
forms of life, though they are probably more abundant 
there. According to Cope, the nicest gradations may be 
traced between some of the extinct mammalian species 
so abundant in the Tertiary deposits of the West—espe- 





956 EVIDENCES OF THE TRUTH OF EVOLUTION. 


=a 


EAD 














id! 
=P aS |e aap 
| 
17 
IV III II I 


Fia. 70.—Transformations of Planorbis (after Hyatt). 


Serics IV. 1, Pl. levis: Undorf. 2, PI. Steinheimensis; 3, tenuis—Stein- 
heimensis; 4, tenuis; 5, discoideus; 6, trochiformis—discoideus ; 7, 
trochiformis: Steinheim. 

Series IIT, 8, Pl. levis: Undorf. 9, Pl. oxystomus; 10, supremus; 11, 
supremus var. turrita: Steinheim. 

Series IT, 12, Pl. levis: Undorf. 138, Pl. crescens—parvus ; 14, 15, cres- 
cens: Steinheim. 

Series J, Sub-series 8. 16, Pl. levis: Undorf. 17, Pl. minutus-levis; 


PROOFS FROM VARIATION OF ORGANIC FORMS. 257 


18, minutus; 19, 20, triquetrus: Steinheim. Swb-series 2. 21, PI. 
minutus; 22, 23, denudatus—minutus; 24, denudatus var. distortus: 
Steinheim. Sub-series 1. 25, Pl. costatus-minutus; 26, costatus ; 
27, 28, costatus var —: Steinheim. 

The specimens from Undorf all belong to an older Tertiary period than 
that at Steinheim. 


cially between the species of the extinct generalized fam- 
ily of Oredontide.* The same is probably true of the 
many extinct species of the horse family. 

It is interesting to observe that the details of the pro- 
cess of change in the forms of Planorbis are in accord 
with Dr. Romanes’s views. The change does not seem 
to hare been uniform but somewhat paroxysmal. The 
forms seem to remain stable for a long time, and then a 
few break into several different forms, while the more 
rigid die out. It is as if cross-breeding had kept the 
type true, but at the same time increased its tendency to 
variation, until finally one or more varieties became sexu- 
ally isolated and thus formed new species. 

5. But still the question remains: Why are transi- 
tional forms rare in all cases, especially between species— 
so rare that they are eagerly sought and highly prized ? 
I believe that the true reason of this is that the steps of 
evolution are not always uniform. 

Nearly all evolutionists have assumed and even in- 
sisted on uniformity, as the opposite of catastrophism 
and of supernaturalism, and therefore as essential to the 
idea of evolution. They say that the constancy of the 


* In a letter to the author, dated February 13, 1887, Prof. Cope says: 
“Such transitions of species are clearly indicated in the Ovcodontida, 
where such different forms as O. gracilis and 0. Culbertsoni are connected 
by intergradations.” 


258 EVIDENCES OF THE TRUTH OF EVOLUTION. 


action of the forces of change necessitates the uniformity 
of the rate of change. But, in fact, this is not always 
nor even usually true. Causes or forces are constant, but 
phenomena everywhere and in every department of Na- 
ture are paroxysmal. The forces producing storms and 
lightning, and volcanoes and earthquakes, are or may be 
constant ; yet the phenomena are in the highest degree 
paroxysmal. Wherever in nature we have a constant 
force and a strong resistance, we find more or less parox- 
ysmal action. For this reason the wind blows in puffs, 
the friction of wind on water produces waves, water run- 
ning in small pipes issues in pulses. ‘The reason is ob- 
vious, as may be seen by the following examples: Sup- 
pose lifting forces within the earth are resisted by crust- 
rigidity. The forces accumulate uniformly until the 
resistance gives way, and suddenly we have an earth- 
quake. Water running with great resistance in small 
pipes is checked, but soon accumulates additional force, 
which overcomes the resistance, only to be again checked, 
and so on, and therefore runs in pulses. Now, the course 
of evolution of the whole earth may be likened to such a 
current ; there are forces of movement and forces of re- 
sistance—progressive forces and conservative forces. The 
progressive force is accumulative, the resisting force is 
constant. Thus, in all evolution or history, whether of the 
earth or of society, there are periods of comparative quiet, 
during which the forces of change are gathering strength, 
and periods of revolution or rapid change, during which 
these forees show themselves in conspicuous effects. 


PROOFS FROM VARIATION OF ORGANIC FORMS. 259 


Now, that there have been such periods of rapid revo- 
lutionary change in the history of the earth, there can be 
no doubt. The history of the earth is marked by periods 
of comparative quiet, during which life was exception- 
ally abundant and prosperous, and change of organic 
forms slow and uniform—separated by periods of dis- 
turbance, revolution, rapid changes of physical geogra- 
phy and climate, and consequently of comparatively rapid 
and sweeping changes in organic forms. These form the 
division-lines between great eras of the earth’s history, 
and are always marked by extensive unconformity of the 
strata, showing the changes of physical geography above 
spoken of, and \y apparently sudden and sweeping 
change in life-forms, showing the great changes of cli- 
mate and other physical conditions. Unfortunately, in 
all cases of unconformity of strata, there is, of course, a 
break in the continuity of the record ; and when the un- 
conformity is very general a portion of the record may 
be irrecoverably lost. The consequence is, that there is 
an apparent break also in the continuity of life-forms. It 
looks, at first sight, like wholesale extermination of old 
and recreation of new forms. But undoubtedly the break 
in the continuity of life is apparent only, as is shown by 
the loss in the record. If we could recover the whole 
record, as indeed we sometimes do, we should find in all 
cases that there is no break in the continuity of evolu- 
tion, but only more rapid rate of change at these times. 
But to this cause of rapid rate of progress—i. e., change 
of physical environment—we must add change of organic 


2960 EVIDENCES OF THE TRUTH OF EVOLUTION. 


environment induced by the physical. We have already 
seen (p. 179) that extensive changes in physical geogra- 
phy and climate are always accompanied by wide migra- 
tions and dispersals of species, the mingling of faunas 
and floras, and the severer struggle for life, and the 
sweeping weeding-out of all but the fittest, and the 
change of these latter, making them still fitter. These 
two causes of rapid change, viz., change of climate and 
migrations, together with the loss of record, we believe 
completely account for those sweeping changes, not only 
of species but even of genera, families, and orders which 
characterize the passage from one great era to another. 

But this does not yet explain the apparent disconti- 
nuity between consecutive species in the same locality in 
continuous, conformable strata, or the rarity of transi- 
tional forms when one species takes the place of another 
in an apparently continuous record. In such continuous 
deposits the successive faunas do indeed gradate insensi- 
bly into one another, but apparently as in contiguous geo- 
graphical regions (p. 200) by substitution, not by trans- 
mutation. How shall we explain this ? 

On this point I throw out some suggestions: 1. In 
the modification of species, too, as well as in other pro- 
gressive changes, we may imagine two forces operating, 
one progressive, the other conservative—the one external, 
the other internal. The external progressive force con- 
sists of all the factors of change already mentioned, the 
internal conservative is the law of heredity, of like pro- 
ducing like. A changing environment tends continually 


PROOFS FROM VARIATION OF ORGANIC FORMS. 261 


and increasingly to change of organisms, but change is 
resisted by heredity, which tends to adhere, within nar- 
row limits, to the same form. But since the external- 
force or tendency to change increases constantly—since 
the discord between the environment and the organism 
becomes ever greater, there must come a time when either 
the species is destroyed, or else the resistance of heredity 
gives way, and rapid change takes place. The alternative 
is presented to the species to transform or perish ; and in 
one or perhaps in two or three generations we have an 
amount of change which, under ,other circumstances, 
might take a hundred generations to accomplish. These 
rapid changes are in fact exactly what in artificial varie- 
ties we call sports. We do not know all the conditions 
which determine sports in domestication, and still less 
what determines large and widely-divergent variations, 
and therefore rapid origin of many divergent species, in 
geological history. But one thing seems probable, viz., 
that, when a species begins to change, it continues to 
change easily and in many directions. When resistance 
gives way it takes some time, many generations, for he- 
redity to gather force again. Hence, young species are 
plastic, fluent, because heredity, on any one point, has 
not yet accumulated. But as soon as a stable form is 
again reached, then, by accumulating a fund of heredity, 
the form tends to become more and more rigid, until 
often it becomes too rigid to yield to modifying influ- 
ences, and therefore becomes extinct. By far the greater 
number of species do thus become extinct and leave no 


962 EVIDENCES OF THE TRUTH OF EVOLUTION. 


progeny, while the few more plastic forms are modified 
in several directions, and the number of forms may, after 
a little time, be undiminished or even increased. 

2. As to the cause of rapid changes of form during 
revolutionary or critical periods in the earth’s history, 
Brooks has introduced an idea which is very suggestive, 
and deserves serious attention. We have above spoken 
of the progressive element as external. Brooks regards 
both elements as internal, and represented by the two 
sexes. The male represents the progressive, the female 
the conservative element. The one tends to divergent 
variation, the other to fixity of type by heredity. I 
think we will all admit that, as a general rule, in man 
(and probably all the higher animals) the male is more 
highly differentiated into many divergent forms—the 
female is more like the type-form of the species. In 
man, the male is certainly more diversified in form, in 
expression, and in character. If they have the keenest 
ear for musical pitch, they are also most often music- 
deaf; if they have the sharpest perception of color, they 
are also most often color-blind ; if among them we find 
the brightest intellects, we also find the dullest and 
most stupid; if there are among them more geniuses, 
so, also, there are more cranks. ‘The same is also, prob- 
ably, true of other animals, in proportion to their grade 
of organization. The operation of these two equally 
necessary elements is well shown in every advancing 
society. The initiative of every movement, in all direc- 
tions, good or bad, is determined by the male; the con- 


PROOFS FROM VARIATION OF ORGANIC FORMS. 263 


servation of whatever balance of good there may be, 
seems to be mainly by the female. ‘The male tries all 
things, the female holds fast that which is good. By 
the one society gains a little in each generation ; by the 
other the gain is conserved and made a new point of 
departure. ‘The one is ever building hastily a scaffold- 
ing and platform; the other ever consolidating into a 
permanent structure. Now, according to Brooks, what 
is true in the plane of social progress is true also in 
the lower plane of organic evolution. In sexual union, 
and in the resulting offspring, the sperm-cell is the 
element which tends to divergent variation, and the 
germ-cell to fixity of type, through heredity. In arti- 
ficial breeding, then, we ought to make new varieties by 
proper use of the sire; we ought to preserve them true 
by proper management of the dam. 

- But, again, it is believed that in many lower ani- 
mals, especially insects, the high-feeding of the mother, 
and consequent good condition of the ovum, tends to 
the production of female offspring. It seems almost 
certain that, in butterflies, the sex is not yet declared 
in the caterpillar stage. According to the careful ex- 
periments of Mrs. Treat,* if the caterpillars be well fed, 
they become female butterflies; but, if poorly fed, they 
make males. One purpose of this provision of Nature 
is, doubtless, to provide for the greater draught on the 
vitality of the female in reproduction. 


* “ American Naturalist,” 1878; “Popular Science Monthly,” June, 
1873. 


964 EVIDENCES OF THE TRUTH OF EVOLUTION. 


Now for the application. In good times in the his- 
tory of a species, when everything is prosperous, external 
conditions are favorable, and food is abundant, females 
are in excess, and individuals are greatly multiplied. 
Under these conditions, evolution would be slow and 
uniform. But in dad times in the history of a species, 
when external conditions were unfavorable, not only 
would there be excess of males, but these, through the 
influence of the changing environment, as well as through 
the dominance of the male element, would be more than 
usually varied in character. Among the strongly diver- 
gent varieties thus formed, the fittest—i. e., those most 
in accord with the changing environment—would sur- 
vive and leave offspring partaking of their character. 
We have already repeatedly said that the severer pressure 
of a rapidly-changing environment determines corre- 
spondingly rapid changes in organic forms. It may do 
so in many ways; but, according to Brooks, one of the 
most important ways is by determining an excess of the 
male element. 

In brief, then, the causes of rarity of transitional 
forms among fossils are—1. The change being, for the 
reasons given, comparatively rapid, the nwmber of gen- 
erations between consecutive species are few, perhaps 
only one. 2. Times of rapid change are also times of 
unfavorable conditions, and therefore the number of 
individuals in each generation is small, and all the 
smaller—in Brooks’s view—because of the fewness of 
females. When we remember that fossils are but a 


PROOFS FROM VARIATION OF ORGANIC FORMS. 265 


small fraction of the actual faunas and floras of the 
time, surely these two causes go far toward explaining 
the rarity of links between species. 3. Add to these 
the existence of periods of wide-spread changes in physi- 
cal geography and climate, and consequent wide migra- 
tions and dispersals of species, and we sufficiently ac- 
count for those sweeping changes in species, genera, 
families, and orders, which mark the limits of the great 
eras, and which are made still more abrupt, and appar- 
ently supernatural, by the loss of record at these times.* 

Objection —There is still one more objection which 
will be made. We have drawings of plants, animals, 
and men, by Egyptian artists, who lived at least three 
thousand years ago, and the species of the one and the, 
races of the other are still the same. Still better, we 
have among the wrappings of Egyptian mummies the 
very plants themselves, leaves and flowers perfectly 
preserved, and even colors almost perfect. Yet the 
species are exactly the same as grow in Egypt to-day. 
If species are made by gradual transmutation, surely 
there ought to have been some change in three thou- 
sand years. 

Answer.—It may be well to note that this apparent 
permanence is true of races of men as well as of spe- 
cies of animals and plants. But the very men who 


* For a fuller development of this subject the reader is referred to 
an article by the author, entitled “‘ Critical Periods in the History of, and 
their Relation to, Evolution” (“‘ American Journal of Science,” vol. xiv, 
p. 99, 1877). 


966. EVIDENCES OF THE TRUTH OF EVOLUTION. 


insist on permanence of species are equally insistent on 
the variability of varieties and races. The objection, 
therefore, proves too much. We shall not insist on this, 
however, because as derivationists we regard races as 
naught else than commencing species, and therefore 
subject to the same laws. We are not striving for tri- 
umph in debate, but only for truth. The true answer 
will, we believe, be found among the following sugges- 
tions : 

1. Three thousand years seems a long time in human 
history, but in geological history it is butaday. This, 
the usual answer, is no doubt a true one, but hardly, 
we think, sufficient. When we remember the enormous 
change which has taken place in faunas and floras since 
the end of the Tertiary, if change still continues at the 
same rate, surely it ought to be distinctly perceptible 
in three thousand years. 

2. But we must remember that such changes are 
usually more or less paroxysmal; not, indeed, so sud- 
den as to break the continuity of lfe, but far more 
rapid at some times than at others. The last critical 
or revolutionary period of rapid change was the Glacial 
epoch. Since that time—i. e., during the human pe- 
riod—a new equilibrium has been established, and the 
changes in organic forms have been very slow. 

3. Remember, again, that in evolution all species 
do not change. On the contrary, most become rigid, 
and either remain unchanged, almost indefinitely, or 
else die out and leave no descendants. Only the more 


PROOFS FROM VARIATION OF ORGANIC FORMS. 267 


plastic forms change into other species, but usually 
into several other species, and thus the number of forms 
may be undiminished, even though the larger number 
of old forms leave no descendants. It is true, there- 
fore, of this as well as of other epochs, that the greater 
number of species are permanent. 

4, It is not impossible—indeed, it is in exact ac- 
cordance with the laws of evolution—that organic forms 
are more permanent now than ever before. Evolution 
is a growth; the forces of growth must exhaust them- 
selves. Evolution proceeds by constant differentiation 
and specialization, but extreme specialization always 
arrests evolution. In ontogenic evolution, for example, 
cell-structure becomes more and more specialized, but 
also thereby more and more rigid, and, when special- 
ization is complete, evolution stops, and cell-forms are 
permanent. It is this which limits the cycle of every 
evolution. So is it precisely with evolution of the or- 
ganic kingdom, except that the cycle is much longer. 
Here, also, every step is by specialization, and yet spe- 
cialization fixes the form, and finally arrests the advance 
on that line. Thus, throughout the whole geological 
history of the earth, the larger number of forms, by 
specialization, become rigid and perish, while the fewer, 
more generalized, and more plastic forms take up the 
march and carry it forward a step, only to be them- 
selves specialized and fixed. If we compare, again, to a 
tree: each twig finishes its growth, flowers, fruits, and 


dies; other buds take up the growth and carry it for- 
19 


968 EVIDENCES OF THE TRUTH OF EVOLUTION. 


ward. By specialization the highest condition of a cer- 
tain form of life is attained, but other possibilities are 
shut off. Extreme specialization is the flowering and 
fruiting—the end and completion of twig-life. Now, 
obviously, this specialization and respecialization can 
not go on forever. When it is complete in every direc- 
tion it must cease, and forms become permanent, or else 
perish. When it flowers it must die. 

Now, is not the advent of man in many ways a sign 
of the completeness of organic evolution ? Certain it 
is that with man there begins an entirely new form of 
evolution. Certain it is that with man evolution is 
transferred from the organic to the social plane, from 
the material to the psychical. Certain it is that the 
forces, the conditions and results of this evolution, are 
wholly different from those of the other. In organic evo- 
lution the organism must conform to the environment; — 
in human evolution the environment is made to conform 
to the wants of the organism. ‘The one is unconscious 
and involuntary, passive under the dominating laws of 
Nature ; the other is conscious, voluntary progress toward 
an ideal, by the wse, among other means, of the laws of 
Nature. The one is by change of external form—i. e., 
change of species—the other by change of brain-struct- 
ure. Now, does not the commencing of the cycle of 
this new evolution imply the closing of that of the old? 
The two may overlap somewhat now, but it is evident 
that, when the cycle of human evolution culminates, 
when highly civilized man shall have taken possession 


PROOFS FROM VARIATION OF ORGANIC FORMS. 269 


of the whole earth, the whole organic kingdom must 
be readjusted to his wants. All organic forms must be 
either domesticated or destroyed. Organic forms will 
no longer be modified by natural but wholly by arti- 
ficial selection. 


There are many other supposed objections which have 
been urged, but these are mostly not objections to evo- 
lution, but only to some special theory of evolution— 
Darwinian, Spencerian, Lamarckian, or other. 

Origin of Beauty.—For example, it has been urged 
that natural selection can only account for useful struct- 
ures ; but beauty is as universal and as conspicuous in 
nature as use. In many cases Darwin has shown that 
beauty is useful, and in such cases it is, of course, 
seized upon by selection and intensified. Thus, the 
gorgeous coloring of birds and insects is largely due 
to sexual selection. Beauty is attractive, and therefore 
the most beautiful prevail in securing reproductive op- 
portunities. This character is, therefore, perpetuated 
in the offspring, and intensified from generation to gen- 
eration. But, of course, this can apply only to higher 
animals, in which the sexes are separate and sexual 
union voluntary. It can not apply to self-fertilizing 
hermaphrodites ; and yet in these, also, we often find 
the most gorgeous coloring. Again, Darwin has very 
ingeniously and successfully explained the case of the 
beauty and fragrance of flowers of hermaphroditic plants 
by another principle, yiz., that of insect-selection. In- 


2970 EVIDENCES OF THE TRUTH OF EVOLUTION. 


sects are attracted by the most showy and fragrant 
flowers, and thus become the means of carrying pollen 
from flower to flower, insuring fertilization, and espe- 
cially cross-fertilization. The most beautiful and fra- 
grant flowers are most certain to be fertilized, and thus 
beauty and fragrance become useful to the plant, and 
therefore are selected and intensified. 

These and many other cases of beauty may doubtless 
be explained by showing that it is useful; but beauty 
which is without any use can not be explained by nat- 
ural selection. Now, as already said, the most gorgeous 
beauty is lavishly distributed even among the lowest 
animals, such as marine shells and polyps, where no such 
explanation is possible. The process by which such 
beauty is originated and intensified is wholly unknown 
to us. 

Incipient Organs.—Again, Mivart has drawn attention 
to another difficulty in the way of natural selection as an 
explanation even of useful organs. Darwin does not, of 
course, attempt to account for the origin of varieties. 
As we have already seen, he assumes divergent variation 
of offspring as the necessary material on which natural 
selection operates. He who shall explain the origin of 
varieties will have made another great step in completing 
the theory of evolution. But not only does not natural 
selection explain the origin of varieties, but neither can 
it explain the first steps of advance toward usefulness. 
An organ must be already useful before natural selection 
can take hold of it to improve it. It can not make it 


PROOFS FROM VARIATION OF ORGANIC FORMS. 971 


useful, but only more useful. For example, if fins com- 
menced as buds from the trunk, it is difficult to see how 
they could be of any use, and therefore how they could 
be improved by natural selection until they were of con- 
siderable size, and especially until muscles were developed 
to move them. Until that time they would seem to be 
a hindrance to be removed by natural selection, instead 
of a use to be preserved and improved. It would seem 
that many organs must have passed through this ¢eipi- 
ent stage, in which their use was prospective. 

Much that is very interesting might be said on these 
and similar points of difficulty, but all this lies entirely 
aside from the scope of this work. As already said, these 
are not objections to evolution or derivation, but only 
to Darwinism, or any other special theory, as a suffictent 
explanation of the process of evolution. They only show 
that we do not yet fully understand this process; that 
there are still other and perhaps greater factors of evolu- | 
tion than is yet dreamed of in our philosophy. 

In the foregoing chapters on special evidences, and 
especially in the last two, the reader will observe many 
points of doubt, discussion, and difference of opinion. 
Let it not be concluded on that account that the law of 
evolution is still in the region of uncertainty. It can 
not be too strongly insisted on that the fact of evolution 
as a universal law must be kept distinct from the causes, 
the factors, the conditions, the processes, of evolution. 
The former is certain, the latter are still imperfectly un- 
derstood. 





Pease ee eee 


THE RELATION OF EVOLUTION TO 
RELIGIOUS THOUGHT. 





CHAPTER I. 
INTRODUCTORY. 


From what has preceded, the reader will perceive 
that we regard the law of evolution as thoroughly estab- 
lished. In its most general sense, i. e., as a law of con- 
tinuity, it is @ necessary condition of rational thought. 
In this sense it is naught else than the universal law of 
necessary causation apphed to forms instead of phe- 
nomena. It is not only as certain as—it is far more 
certain than—the law of gravitation, for it is not a con- 
tingent, but a necessary truth like the axioms of geome- 
try. It is only necessary to conceive it clearly, to accept 
it unhesitatingly. The consensus of scientific and phil- 
osophical opinion is already well-nigh, if not wholly, 
complete. If there are still lingering cases of dissent 
among thinking men, it is only because such do not yet 
conceive it clearly—they confound it with some special 
form of explanation of evolution which they, perhaps 
justly, think not yet fully established. We have some- 
times in the preceding pages used the words evolutionist 
or derivationist ; they ought not to be used any longer. 
The day is past when evolution might be regarded asa 


276 EVOLUTION AND RELIGIOUS THOUGHT. 


school of thought. We might as well talk of gravita- 
tionist as of evolutionist. 

If, then, evolution as a law be certain, if, moreover, 
it is a law affecting not only one part of Nature—the 
organic kingdom—and one department of science—bio- 
logy—but the whole realm of Nature and every depart- 
ment of science, yea, every department of thought, 
changing our whole view of Nature and modifying our 
whole philosophy, the question presses upon us, *‘ What 
will be its effect on religious belief, and therefore on 
moral conduct ?” ‘This is a question of gravest import. 
To answer it, however imperfectly, is the chief object of 
this work. Except for this, it would probably never 
have been undertaken. All that goes before is sub- 
sidiary to this. 

But I will doubtless be met at the very threshold by 
an objection from the scientific side. Some will say— 
because it is the fashion: now to say—that as simple, 
honest truth-seekers, we have nothing to do with its 
effect on religion and on life. They say we must follow 
Truth wherever she leads, utterly regardless of what may 
seem to us moral consequences. ‘This I believe is a grave 
mistake, the result of a reaction, and on the whole a 
wholesome and noble reaction, against the far more com- 
‘mon mistake of sacrificing truth to a supposed good. 
But the reaction, as in most other cases, has gone much 
too far. There is a true philosophic ground of justifica- 
tion for the reluctance with which even honest truth- 
seekers accept a,doctrine which seems harmful to so- 


INTRODUCTORY. 27 


ciety. Effect on life is, and ought to be, an important — 
element in owr estimate of the truth of any doctrine. It 
is necessary for me to show this, in order to justify this 
part of my work. 

Relation of the True and the Good.—There is a ne- 
cessary and indissoluble connection between truth and 
usefulness. We all at once admit this connection in one 
direction. We all admit that a truth must eventually 
have its useful application. It may not be now, nor in 
ten years, nor in a century, nor even in a millennium, 
but some time in the future it will vindicate its useful- 
ness. No truth is trivial or useless in its relation to 
human life, for man is a part of Nature, and his life must 
be in accordance with the laws of Nature. Every one 
admits this, but not every one admits the converse 
proposition, viz., that whatever doctrine or belief, in the 
long run and throughout the history of human advance- 
ment, has tended to the betterment of our race, must 
have in it an element of truth by virtue of which it has 
been useful ; for man’s good can not be in conflict with 
the laws of Nature. Also, whatever in the long run and 
in the final outcome tends to the bad in human conduct, — 
ought to be received, even by the honest truth-seeker, 
with distrust as containing essential error. The reason 
of this will now be further explained. 

Relation of Philosophy to Life—There are three pri- 
mary divisions of our psychical nature, viz., sensuous, 
intellectual, and volitional or moral. There are three 
corresponding primary processes necessary to make a 


978 EVOLUTION AND RELIGIOUS THOUGHT. 


aed 


complete rational and satisfactory philosophy: (1) There 
is first the ¢xstreaming of the external world through the 
senses, as impressions. These we call facts or phenome- 
na. (2) The elaboration of these facts within, by the in- 
tellect, into a compact, consistent structure. ‘This we call 
knowledge. (8) The outgoing of this knowledge by the 
will into the world as right or wise conduct. Now these 
three are all equally necessary. All these three portions 
of our complex nature are equally urgent to be satisfied.* 
But, unfortunately, scientific workers are too apt to 
think only 1 and 2 necessary—that true facts elaborated 
into consistent theory are all we need care for. ‘Theo- 
logians and metaphysicians, on the other hand, seem to 
think only 2 and 3 necessary. They elaborate a theory 
consistent in all its parts, exquisitely woven in beautiful 
and delicate pattern, and apparently satisfactory in its 
application to the right conduct of life, but are less 
careful to inquire whether it is in harmony with facts 
derived from the senses. But, we repeat, all three are 
equally necessary. ‘The first gathers the materials, the 
second constructs the edifice, the third, by wse, by prac- 
tical application, tests whether it be a fit building to live 
in, whether it is constructed on sound architectural prin- 
ciples. The tendency of the olden time was to neglect 
the first, the tendency of the present time is to neglect 
the third. But we repeat with stronger emphasis that this 
third element is equally necessary. All admit that suc- 





* “ Reflex Action and Theism,” William James, “ Unitarian Review” 
for November, 1881. 


INTRODUCTORY. 279 


cessful application in art is the surest test of the truth 
of science. Now, social conduct is the art correspond- 
ing to our philosophy of life, and therefore is the sure 
test of its truth. It follows, therefore, that unless all 
these three primary divisions of our nature are satis- 
fied by any doctrine, there must result an ineradicable 
confusion and discord in our psychical nature, and cor- 
dial acceptance is not only impossible but irrational. 
We insist upon this the more because it has become the 
fashion in these latter days of dominance of science, to 
say that to inquire into effects on society is inconsistent 
with the scientific spirit, and unworthy of the honest 
truth-seeker. But, observe, I am speaking of effects on 
society only as a test of truth. I would not swerve a 
hair’s breadth from absolute devotion to truth. It is 
necessary, indeed, to inquire into effects on society, but 
we must inquire only in the patient spirit characteristic 
of the truth-seeker. Whatever is really true will surely 
vindicate itself by its bencficence, if we will only wait 
patiently for final results. Evolution is no exception 
to this universal truth. It will surely vindicate its 
beneficence, but we must wait yet a little while—not very 
long. 

So much it was necessary to say in justification of the 
inquiry which constitutes this third part of our work. 
But, after this justification, the question returns with 
additional emphasis, ‘‘ What will be the effect of the 
universal acceptance of the law of evolution on religious 
thought, and through this on the right conduct of life ?” 


280 EVOLUTION AND RELIGIOUS THOUGHT. 


There can be no doubt that evolution, as a law affect- 
ing all science and every department of Nature, must 
fundamentally affect the whole realm of thought, and pro- 
foundly modify our traditional views of Nature, of God, 
and of man. ‘There can be no doubt that we are now on 
the eve of a great revolution. But, as in all great revo- 
lutions, so in this, the first fears as to its effects are 
greatly exaggerated. ‘To many, both friends and foes of 
Christianity, evolution seems to sweep away the whole 
foundation, not only of Christianity, but of all religion 
and morals, by demonstrating a universal materialism. 
Many are ready to cry out in anguish, ‘‘ Ye have taken 
away our gods, what have we more? Ye have destroyed 
our dearest hopes and noblest aspirations, what more 
is left worth living for?” But I think all who are at all 
familiar with the history of the so-called conflict between 
religion and science will admit this is not the first time 
this cry has been raised against science. They have 
heard this danger-cry so often that they begin to regard 
it as little more than a wolf-cry—scientific wolf in the 
religious fold. It may not be amiss, then, to stop a mo- 
ment to trace rapidly the main points of this conflict—to 
discuss the various forms of this scientific wolf. 

First, then, it came in the form of the heliocentric 
theory of the planetary system. We once thought the 
earth the center of the universe, and so firm that it can 
not be moved. But science shows that it moves about 
the sun, and spins unceasingly on its axis, Every one 
has heard of the terror of the sheep produced by this dis- 


INTRODUCTORY. 281 


covery, and the nearly tragic results to the bold scientist. 
But now we look back with wonder that there should 
have been any trouble at all. Would any Christian now 
consent to give up the grand conceptions of Nature and 
of God thus opened to the human mind—the idea of 
infinite space full of worlds, of which our earth is one, 
moving in silent harmony as in a mystic dance? Verily, 
this wolf has proved itself a harmless, nay, a very noble 
beast, and lies down in peace with the lambs. 

Next, it came in the shape of the law of gravitation, 
as sustentation of the cosmos by law and resident forces. 
The effect of this on religious thought was even more 
profound, though less visible on the surface, because only 
perceived by the most intelligent. It seemed at that time 
to remove God from the course of Nature. This was the 
real ground of the skepticism of the last century, and 
also the real motive of Voltaire’s ardent advocacy of 
Newton’s views before these were generally accepted in 
France. But now, who would give up this grand idea— 
this conception of law pervading infinite space—the same 
law which controls the falling of a stone guiding also the 
planetary orbs in their fiery courses ? This is indeed the 
divine spheral music, inaudible but to the ear of science, 
accompanying the celestial dance. 

Next, it came in the form of the antiquity of the earth 
and of the cosmos. The earth which we had fondly 
thought made specially for us about six thousand years 
ago; sun, moon, and stars, which we had vainly imagined 
shone only for our behoof—these, science tells us, existed 


982 EVOLUTION AND RELIGIOUS THOUGHT. 


and each performed its due course inconceivable ages 
before there was a man to till the ground or contemplate 
the heavens. Some of my readers may still remember 
the horror, the angry dispute which followed the pro- 
mulgation of these facts. But now, who would consent 
to give up the noble conception of infinite time thus 
opened to the human mind and become forever the heri- 
tage of man ? 

Next, it came in the form of the antiquity of man. 
It is probable, nay, certain, that man has inhabited the 
earth far longer than we had previously supposed we had 
warrant for believing. The controversy on this question 
and the dread of its result has indeed not yet entirely 
subsided. Some timid people still look askance at this 
wolf, but I think all intelligent people accept it and find 
it harmless. 

Next, and last, it comes now in the form of evolution 
—of the origin of all things, even of organic forms, by de- 
rivation—of creation by law. We are even now in the 
midst of the terror created by this doctrine. But what 
is evolution but law throughout infinite time? The 
same law which now controls the development of an egg 
has presided over the creation of worlds. Infinite space 
and the universal law of gravitation ; infinite time and the 
universal law of evolution. These two are the grandest 
ideas in the realm of thought. The one is universal sus- 
tentation, the other universal creation, by law. There 
is one law and one energy pervading all space and stretch- 
ing through all time. Our religious philosophy has long 


INTRODUCTORY. 2835 


ago accepted the one, but has not yet had time to re- 
adjust itself completely to the other. A few more years, 
and Christians will not only accept, but love and cherish 
this also for the noble conceptions it gives of Nature and 
of God. 

But some will exclaim, ‘‘ Noble conceptions of God, 
say you! Why, it utterly obliterates the idea of God 
from the mind. All other conflicts were for outworks— 
this strikes at the citadel. All others required only re- 
adjustment of claims, rectification of boundaries betwixt 
science and religion—this requires nothing less than un- 
conditional surrender. Evolution is absolute material- 
ism, and materialism is incompatible with belief in God, 
and therefore with religion of any kind whatsoever !” 
Before proceeding any further, it becomes necessary to 
remove this difficulty out of the way. 


20 


CHAPTER II. 
THE RELATION OF EVOLUTION TO MATERIALISM. 


It is seen in the sketch given in the previous chapter 
that, after every struggle between theology and science, 
there has been a readjustment of some beliefs, a giving 
up of some notions which really had nothing to do with 
religion in a proper sense, but which had become so 
associated with religious belief as be to confounded with 
the latter—a giving up of some line of defense which 
ought never to have been held because not within the 
rightful domain of theology at all. Until the present 
the whole difficulty has been the result of misconception, 
and Christianity has emerged from every struggle only 
strengthened and purified, by casting off an obstructing 
shell which hindered its growth. But the present strug- 
gle seems to many an entirely different and far more 
serious matter. To many it seems no longer a struggle 
of theology, but of essential religion itself—a deadly 
life-and-death struggle between religion and materialism. 
To many, both skeptics and Christians, evolution seems 
to be synonymous with blank materialism, and therefore 
cuts up by the roots every form of religion by denying 


RELATION OF EVOLUTION TO MATERIALISM. 985 


the existence of God and the fact of immortality. That 
the enemies of religion, if there be any such, should 
assume and insist on this identity, and thus carry over 
the whole accumulated evidence of evolution as a dem- 
onstration of materialism, although wholly unwarrant- 
ed, is not so surprising; but what shall we say of the 
incredible folly of her friends in admitting the same 
identity ! 

A little reflection will explain this, There can be no 
doubt that there is at present a strong and to many an 
overwhelming tendency toward materialism, The amaz- 
ing achievements of modern science ; the absorption of 
intellectual energy in the investigation of external nature 
and the laws of matter have created a current in that di- 
rection so strong that of those who feel its influence—of 
those who do not stay at home, shut up in their creeds, 
but walk abroad in the light of modern thought—it 
sweeps away and bears on its bosom all but the strongest 
and most reflective minds. Materialism has thus become 
a fashion of thought; and, like all fashions, must be 
guarded against. This tendency has been created and 
is now guided by science. Just at this time it is strong- 
est in the department of biology, and especially is evo- 
lution its stronghold. This theory is supposed by many 
to be simply demonstrative of materialism. Once it was 
the theory of gravitation which seemed demonstrative of 
materialism. The sustentation of the universe by law 
seemed to imply that Nature operates itself and needs no 
God. That time is passed. Now it is evolution and 


986 EVOLUTION AND RELIGIOUS THOUGHT. 


creation by law. ‘This will also pass.) The theory seems 
to many the most materialistic of all scientific doctrine 
only because it is the Jast which is claimed by material- 
ism, and the absurdity of the claim is not yet made 
clear to many. 

The truth is, there is no such necessary connection 
between evolution and materialism as is imagined by 
some. There is no difference in this respect between 
evolution and any other law of Nature. In evolution, it 
is true, the last barrier is broken down, and the whole 
domain of nature is now subject to law; but it is only 
the last ; the march of science has been in the same di- 
rection all the time. In a word, evolution is not only 
not identical with materialism, but, to the deep thinker, 
it has not added a feather’s weight to its probability or 
reasonableness. Evolution is one thing and materialism 
quite another. The one is an established law of na- 
ture, the other an unwarranted and hasty inference from 
that law. Let no one imagine, as he is conducted by 
the materialistic scientist in the paths of evolution from 
the inorganic to the organic, from the organic to the 
animate, from the animate to the rational and moral, 
until he lands, as it seems to him, logically and inevita- 
bly, in universal materialism—let no such one imagine 
that he has walked all the way in the domain of science. 
He has stepped across the boundary into the domain of 
philosophy. But, on account of the strong tendency to 
materialism and the skillful guidance of his leaders, 
there seems to be no such boundary; he does not dis- 


RELATION OF EVOLUTION TO MATERIALISM. 287 


tinguish between the inductions of science and the in- 
ferences of a shallow philosophy; the whole is accredited 
to science, and the final conclusion seems to carry with 
it all the certainty which belongs to scientific results. 
The fact that these materialistic conclusions are reached 
by some of the foremost scientists of the present day 
adds nothing to their probability. In a question of sci- 
ence, viz., the law of evolution, their authority is de- 
servedly high, but in a question of philosophy, viz., 
materialism, it is far otherwise. If the pure scientists 
smile when theological philosophers, unacquainted with 
the methods of science, undertake to dogmatize on the 
subject of evolution, they must pardon the philosophers 
if they also smile when the pure scientists imagine that 
they can at once solve questions in philosophy which 
have agitated the human mind from the earliest times. 
I am anxious to show the absurdity of this materialistic 
conclusion, but I shall try to do so, not by any labored 
argument, but by a few simple illustrations. 

1. It is curious to observe how, when the question 
is concerning a work of Nature,.we no sooner find out 
how a thing is made than we immediately exclaim : “ It 
is not made at all, it became so of itself!” So long as 
we knew not how worlds were made, we of course con- 
cluded they must have been created, but so soon as sci- 
ence showed how it was probably done, immediately we 
say we were mistaken—they were not made at all. So 
also, so long as we could not imagine how new organic 
forms originated, we were willing to believe they were 


988 EVOLUTION AND RELIGIOUS THOUGHT. 


created, but, so soon as we find that they originated by 
evolution, many at once say, ‘‘We were mistaken ; no 
creator is necessary at all.” Is this so when the question 
is concerning a work of man? Yes, of one kind—yiz., 
the work of the magician. Here, indeed, we believe in 
him, and are delighted with his work, until we know 
how it is done, and then all our faith and wonder cease. 
But in any honest work it is not so; but, on the con- 
trary, when we understand how it is done, stupid wonder 
is changed into intellectual delight. Does it not seem, 
then, that to most people God is a mere wonder-worker, 
a chief magician. But the mission of science is to show 
us how things are done. Is it any wonder, then, that to 
such persons science is constantly destroying their super- 
stitious illusions ? But if God is an honest worker, ac- 
cording to reason—i.e., according to law—ought not 
science rather to change gaping wonder into intelligent 
delight—superstition into rational worship ? 

2. Again, it is curious to observe how an old truth, 
if it come only in a new form, often strikes us as some- 
thing unheard of, and even as paradoxical and almost 
impossible. <A little over thirty years ago a little philo- 
sophical toy, the gyroscope, was introduced and became 
very common. At first sight, it seems to violate all me- 
chanical laws, and set at naught the law of gravitation 
itself. A heavy brass wheel, four to five inches in diame- 
ter, at the end of a horizontal axle, six or eight inches 
long, is set rotating rapidly, and then the free end of the 
axis is supported by a string or otherwise. The wheel re- 


RELATION OF EVOLUTION TO MATERIALISM. 989 


mains suspended in the air while slowly gyrating. What 
mysterious force sustains the wheel when its only point of 
support is at the end of the axle, six or eight inches 
away ? Scientific and popular literature were flooded 
with explanations of this seeming paradox. And yet it | 
was nothing new. The boy’s top, that spins and leans 
and will not fall, although solicited by gravity, so long 
as it spins, which we have seen all our lives without spe- 
cial wonder, is precisely the same thing. 

Now, evolution is no new thing, but an old familiar 
truth ; but, coming now in a new and questionable shape, 
lo, how it startles us out of our propriety! Origin of 
forms by evolution is going on everywhere about us, both 
in the inorganic and the organic world. In its more fa- 
miliar forms, it had never occurred to most of us that it 
was a scientific refutation of the existence of God, that it 
was a demonstration of materialism. But now itis pushed 
one step farther in the direction it has always been going 
—it is made to include also the origin of species—only a 
little change in its form, and lo, how we start! To the 
deep thinker, now and always, there is and has been the 
alternative—materialism or theism. God operates Nature 
or Nature operates itself; but evolution puts no new 
phase on this old question. For example, the origin 
of the individual by evolution. Everybody knows that 
every one of us individually became what we now are by 
a slow process of evolution from a microscopic spherule 
of protoplasm, and yet this did not interfere with the 
idea of God as our individual maker. Why, then, should 


290 EVOLUTION AND RELIGIOUS THOUGHT. 


the discovery that the species (or first individuals of each 
kind) originated by evolution destroy our belief in God 
as the creator of species ? 

3. It is curious and very interesting to observe the 
manner in which vexed questions are always finally set- 
tled, if settled at all. All vexed questions—i. e., ques- 
tions which have tasked the powers of the greatest minds 
age after age—are such only because there is a real truth 
on both sides. Pure, unmixed error does not live to 
plague us long. Error, when it continues to live, does 
so by virtue of a germ of truth contained. Great ques- 
tions, therefore, continue to be argued pro and con from 
age to age, because each side is in a sense—i. e., from its 
own point of view—true, but wrong in excluding the 
other point of view; and a true solution, a true rational 
philosophy, will always be found in a view which com- 
bines and reconciles the two partial, mutually excluding 
views, showing in what they are true and in what they are 
false—explaining their differences by transcending them. 
This is so universal and far-reaching a principle that I 
am sure I will be pardoned for illustrating it in the 
homeliest and tritest fashion. JI will do so by means 
of the shield with the diverse sides, giving the story 
and construing it, however, in my own way. ‘There is, 
apparently, no limit to the amount of rich marrow of 
truth that may be extracted from these dry bones of 
popular proverbs and fables by patient turning and 
gnawing. 

We al! remember, then, the famous dispute concern- 


RELATION OF EVOLUTION TO MATERIALISM. 291 


ing the shield, with its sides of different colors, which 
we shall here call white and black. We all remember 
how, after vain attempts to discover the truth by dis- 
pute, it was agreed to try the scientific method of investi- 
gation. We all remember the surprising result. Both 
parties to the dispute were right and both were wrong. 
Each was right from his point of view, but wrong in 
excluding the other point of view. Hach was right in 
what he asserted, and each wrong in what he denied. 
And the complete truth was the combination of the 
partial truths and the elimination of the partial errors. 
But we must not make the mistake of supposing that 
truth consists in compromise. There is an old adage 
that truth les in the middle between antagonistic ex- 
tremes. But it seems to us that this is the place of 
safety, not of truth. This is the favorite adage, there- 
fore, of the timid man, the time-server, the fence-man, 
not the truth-seeker. Suppose there had been on the 
occasion mentioned above one of these fence-philoso- 
phers. He would have said: ‘‘ These disputants are 
equally intelligent and equally valiant. One side says 
the shield is white, the other that it is black, now truth 
lies in the middle; therefore, I conclude the shield is 
gray or neutral tint, or a sort of pepper-and-salt.” Do 
we not see that he is the only man who has no truth in 
him? No; truth is no heterogeneous mixture of oppo- 
site extremes, but a stereoscopic combination of two sur- 
face views into one solid reality. 

Now, the same is true of all vexed questions, and I 


2992 EVOLUTION AND RELIGIOUS THOUGHT. 


have given this trite fable again only to apply it to the 
case in hand. 

There are three possible views concerning the origin 
of organic forms whether individual or specific. Two of 
these are opposite and mutually excluding ; the third 
combining and reconciling. For example, take the in- 
dividual. ‘here are three theories concerning the ori- 
gin of the individual. The first is that of the pious 
child who thinks that he was made very much as he 
himself makes his dirt-pies; the second is that of the 
street-gamin, or of Topsy, who says: ‘“‘I was not made 
at all, I growed”; the third is that of most intelligent 
Christians—i. e., that we were made by a process of eyvo- 
lution. Observe that this latter combines and reconciles 
the other two, and is thus the more rational and philo- 
sophical. Now, there are also three exactly correspond- 
ing theories concerning the origin of species. The first is 
that of many pious persons and many intelligent clergy- 
men, who say that species were made at once by the Di- 
vine hand without natural process. The second is that 
of the materialists, who say that species were not made at 
all, they were derived, ‘‘they growed.” The third is that 
of the theistic evolutionists, who think that they were 
created by a process of evolution—who believe that mak- 
ing is not inconsistent with growing. The one asserts 
the divine agency, but denies natural process; the second 
asserts the natural process, but denies divine agency; the 
third asserts divine agency by natural process. Of the 
first two, observe, both are right and both wrong; each 


RELATION OF EVOLUTION TO MATERIALISM, 293 


view is right in what it asserts, and wrong in what it 
denies—each is right from its own point of view, but 
wrong in excluding the other point of view. The third 
is the only true rational solution, for it includes, com- 
bines, and reconciles the other two; showing wherein 
each is right and wherein wrong. It is the combination 
of the two partial truths, and the elimination of the par- 
tial errors. But let us not fail to do perfect justice. 
The first two views of origin, whether of the individual 
or of the species, are indeed both partly wrong as well as 
partly right ; but the view of the pious child and of the 
Christian contains by far the more essential truth. Of 
the two sides of the shield, theirs is at least the whiter 
and more beautiful. 

But, alas! the great bar to a speedy settlement of 
this question and the adoption of a rational philosophy 
is not in the head but in the heart—is not in the reason 
but in pride of opinion, self-conceit, dogmatism. The 
rarest of all gifts is a truly tolerant, rational spirit. In 
all our gettings let us strive to get this, for 7 alone is 
true wisdom. But we must not imagine that all the 
dogmatism is on one side, and that the theological. 
Many seem to think that theology has a ‘‘ pre-emptive 
right” to dogmatism. If so, then modern materialistic 
science has ‘‘jumped the claim.” Dogmatism has its 
roots deep-bedded in the human heart. It showed itself 
first in the domain of theology, because there was the 
seat of power. In modern times it has gone over to the 
side of science, because here now is the place of power 


294 EVOLUTION AND RELIGIOUS THOUGHT. 


and fashion. There are two dogmatisms, both equally 
opposed to the true rational spirit, viz., the old theologi- 
cal and the new scientific. The old clings fondly to 
old things, only because they are old; the new grasps 
eagerly after new things, only because they are new. 
True wisdom and true philosophy, on the contrary, tries 
all things both old and new, and holds fast only to that 
which is good and true. The new dogmatism taunts the 
old for credulity and superstition; the old reproaches 
the new for levity and skepticism. But true wisdom 
perceives that they are both equally credulous and equal- 
ly skeptical. The old is credulous of old ideas and 
skeptical of new; the new is skeptical of old ideas and 
credulous of new. Both deserve the unsparing rebuke 
of all right-minded men. ‘The appropriate rebuke for 
the old dogmatism has been already put in the mouth 
of Job in the form of a bitter sneer: ‘‘ No doubt ye are 
the people, and wisdom shall die with you.” The ap- 
propriate rebuke for the new dogmatism, though not put 
into the mouth of any ancient prophet, ought to be ut- 
tered—I wil) undertake to utter it here. I would say to 
these modern materialists, ‘No doubt ye are the men, 
and wisdom and true philosophy were dorn with you.” 
Let it be observed that we are not here touching the 
general question of the personal agency of God in operat- 
ing Nature. This we shall take up hereafter. All that 
we wish to insist on now is that the process and the law 
of evolution does not differ in its relation to materialism 
from all other processes and laws of Nature. If the 


RELATION OF EVOLUTION TO MATERIALISM. 995 


sustentation of the universe by the law of gravitation 
does not disturb our belief in God as the sustainer of 
the universe, there is no reason why the origin of the 
universe by the law of evolution should disturb our 
faith in God as the ereator of the universe. If the law 
of gravitation be regarded as the Divine mode of susten- 
tation, there is no reason why we should not regard the 
law of evolution as the Divine process of creation. It is 
evident that if evolution be materialism, then is grav- 
itation also materialism; then is every law of Nature 
and all science materialism. If there be any difference 
at all, it consists only in this: that, as already said, here 
is the /as¢ line of defense of the supporters of supernatu- 
ralism in the realm of Nature. But being the last line 
of defense—the last ditch—it is evident that a yielding 
here implies not a mere shifting of line, but a change 
of base ; not a readjustment of details only, but a recon- 
struction of Christian theology. This, I believe, is in- 
deed necessary. There can be little doubt in the mind 
of the thoughtful observer that we are even now on the 
eve of the greatest change in traditional views that has 
taken place since the birth of Christianity. But let no 
one be greatly disturbed thereby. For as then, so now, 
change comes not to destroy but to fulfill all our dearest 
hopes and aspirations; as then, so now, the germ of 
living truth has, in the course of ages, become so en- 
crusted with meaningless traditions which stifle its 
growth, that it is necessary to break the shell to set it 
free ; as then, so now, it has become necessary to purge 


296 EVOLUTION AND RELIGIOUS THOUGHT. 


religious belief of dross in the form of trivialities and 
superstitions. ‘This has ever been and ever will be the 
function of science. The essentials of religious faith it 
does not, it can not, touch, but it purifies and ennobles 
our conceptions of Deity, and thus elevates the whole 
plane of religious thought. 

It will not, of course, be expected of me to give, even 
in briefest outline, a system of reconstructed Christian 
thought. Such an attempt would be wholly unbecoming. 
Time, very much time, and the co-operation of many 
minds, bringing contributions from many departments 
of thought, is necessary for this. In a word, it can only 
itself come by a gradual process of evolution. But from 
the point of view of science some very fundamental 
changes in traditional views are already plain. Of these 
the most fundamental and important are our ideas con- 
cerning God, Nature, and man in their relations to one 
another. These will form the subject of the next three 
chapters. | 


CHAPTER III. 
THE RELATION OF GOD TO NATURE. 


We have already said that evolution does not differ 
essentially from other laws of Nature in its bearing on 
religious belief. It only reiterates and enforces with 
additional emphasis what Science, in all its departments, 
has been saying all along. ‘The difficulties in the way of 
certain traditional views have pressed with ever increas- 
ing force upon the thoughtful mind ever since the birth 
of modern science. All along, an issue has been gather- 
ing, but put off from time to time by compromise, until 
now, at last, the issue is forced upon us and compromise 
is exhausted. The issue (let us look it squarely in the 
face) is: Either God is far more closely related with Na- 
ture, and operates it In a more direct way than we have 
recently been accustomed to think, or else (mark the al- 
ternative) Nature operates itself and needs no God at 
all. There is no middle ground tenable. 

Let us trace rapidly the growth of this issue. The 
old idea and the most natural to the religious mind was 
the direct agency of God in every event and phenomenon 
of Nature. ‘This view is nobly expressed in the noblest 


298 EVOLUTION AND RELIGIOUS THOUGHT. 


literature in the world—in the Hebrew and Christian 
Scriptures: ‘‘ He looketh on the earth and it trembleth. 
He toucheth the hills and they smoke.” ‘‘ He maketh 
his sun to rise on the evil and on the good, and sendeth 
his rain on the just and on the unjust.” But now comes 
Science and explains all these phenomena by natural laws 
and resident forces, and we all accept her explanation. 
Thus, one by one the phenomena of Nature are explained 
by the operation of resident forces according to natural 
laws, until the whole course of Nature, as we now know 
it, has been, or will be, or conceivably may be, thus ex- 
plained. 

Thus has gradually grown up, without our confessing 
it, a kind of scientific polytheism—one great Jehovah, 
perhaps, but with many agents or sub-gods, each inde- 
pendent, efficient, and doing all the real work in his own 
domain. The names of these, our gods, are gravity, light, . 
heat, electricity, magnetism, chemical affinity, etc., and 
we are practically saying: ‘‘These be your gods, O 
Israel, which brought you out of the land of Egyptian 
darkness and ignorance. ‘These be the only gods ye 
need fear, and serve, and study the ways of.” 

What, then, is practically the notion which most 
people seem to have of the relation of Deity to Nature ? 
It is that of a great master-mechanic far away above us 
and beyond our reach, who once upon a time, long ago, 
and once for all, worked, created matter, endowed it with 
necessary properties and powers, constructed at once out 
of hand this wonderful cosmos with its numberless 


THE RELATION OF GOD TO NATURE. 299 


wheels within wheels, endowed it with forces, put springs 
in it, wound it up, set it a-going, and then—rested. 
The thing has continued to go of itself ever since. He 
might have not only rested but slept, and the thing 
would have gone of itself. He might not only have 
slept but died, and still the thing would have continued 
to go of itself. But, no, I forget. He must not sleep or 
die, for the work is not absolutely perfect. ‘There are 
some things too hard even for Him to do in this master- 
ful, god-like way. There are some things which even He 
can not do except in a ’prentice-like, man-like way. The 
hand must be introduced from time to time to repair, to 
rectify, to improve, especially to introduce new parts, 
such as new organic forms. 

Such was the state of the compromise until twenty- 
five years ago. Nature is sufficient of itself for its course 
and continuance, but not for origins of at least some new 
parts. Such was the state of the compromise until Dar- 
win and the theory of evolution. But, now, even this 
poor privilege of occasional interference is taken away. 
Now, origins, as well as courses, are reduced to resident 
forces and natural law. Now, Nature is sufficient of it- 
self, not only for sustentation, but also for creation. 
Thus, Science has seemed to push Him farther and far- 
ther away from us, until now, at last, if this view be 
true, evolution finishes the matter by pushing Him en- 
tirely out of the universe and dispensing with Him alto- 
gether. This, of course, is materialism. But this is no 


new view now brought forward for the first time by evo- 
21 


800 EVOLUTION AND RELIGIOUS THOUGHT. 


lution. On the contrary, evolution only finishes what 
“science has been doing all along. 

See, then, how the issue is forced. Either Nature is 
sufficient of itself and wants no God at all, or else this 
whole idea, the history of which we have been tracing, is 
radically false. We have here given by science either a 
demonstration of materialism or else a reductio ad ab- 
surdum. Whichis it? I do not hesitate a moment to 
say it is a reductio ad absurdum. And I believe that 
evolution has conferred an inestimable benefit on phi- 
losophy and on religion by forcing this issue and com- 
pelling us to take a more rational view. 

What, then, is the alternative view ? It is the utter 
rejection with Berkeley and with Swedenborg of the in- 
dependent existence of matter and the real efficient 
agency of natural forces. It is the frank return to the 
old idea of direct divine agency, but in a new, more ra- 
tional, less anthropomorphic form. It is the bringing 
together and complete reconciliation of the two appar- 
ently antagonistic and mutually excluding views of di- 
rect agency and natural law. Such reconciliation we 
have already seen is the true test of a rational philosophy. 
It is the belief in a God not far away beyond our reach, 
who once long ago enacted laws and created forces which 
continue of themselves to run the machine we call Na- 
ture, but a God immanent, a God resident 72 Nature, 
at all times and in all places directing every event and 
determining every phenomena—a God in whom in the 
most literal sense not only we but all things have their 


THE RELATION OF GOD TO NATURE. 301 


being, in whom all things consist, through whom all 
things exist, and without whom there would be and could 
be nothing. According to this view the phenomena of 
Nature are naught else than objectified modes of divine 
thought, the forces of Nature naught else than different 
forms of one omnipresent divine energy or will, the 
laws of Nature naught else than the regular modes of 
operation of that divine will, invariable because He is 
unchangeable. According to this view the law of gravi- 
tation is naught else than the mode of operation of the 
divine energy in sustaining the cosmos—the divine meth- 
od of sustentation; the law of evolution naught else 
than the mode of operation of the same divine energy 
in originating and developing the cosmos—the divine 
method of creation ; and Science is the systematic knowl- 
edge of these divine thoughts and ways—a rational sys- 
tem of natural theology. In a word, according to this 
view, there is no real efficient force but spirit, and no 
real independent existence but God. 

But some will object that this is pure /dealism. Yes, 
but far different from what usually goes under that 
name. ‘The ideal philosophy as usually understood re- 
gards the external world as having no real objective ex- 
istence outside of owrselves—as objectified mental states 
of the observer—as literally such stuff as dreams are made 
of—as a mere phantasmagoria of trooping shadows hay- 
ing no real existence but in the mind of the dreamer, 
and each dreamer makes his own world. Not so in the 
idealism above presented. According to this the exter- 


302 EVOLUTION AND RELIGIOUS THOUGHT. 


nal world is the objectified modes, not of the mind of 
the observer, but of the mind of God. According to 
this, the external world is not a mere unsubstantial fig- 
ment or dream, but for ws a very substantial objective 
reality surrounding us and conditioning us on every 
side. 

Again, it will be objected that this is pure Pantheism. 
Again, we answer “‘yes.” Call it so if you like, but far 
different from what goes under that name, far different 
from the pantheism which sublimates the personality of 
the Deity into all-pervading unconscious force, and 
thereby dissipates all our hopes of personal relation with 
him. Properly understood, we believe this view com- 
pletely reconciles the two antagonistic and mutually ex- 
cluding views of impersonal pantheism and anthropomor- 
phic personalism, and is therefore more rational than 
either. The discussion of this most important point can 
only come up after the next chapter, because the argu- 
ment for the personality of Deity is derived, not from 
without by the study of Nature, but from within in our 
own consciousness. We therefore put off its discussion 
for the present. 

But, finally, some will object, ‘‘ We can not live and 
work effectively under such a theory unless, indeed, we 
escape through pantheism.” It may, alas! be true that 
this view brings us too near Him in our sense of spiritual 
nakedness and shortcoming. It may, indeed, be that we 
can not live and work in the continual realized presence 
of the Infinite. It may, indeed, be that we must still 


THE RELATION OF GOD TO NATURE. 303 


wear the veil of a practical materialism on our hearts and 
minds. It may, indeed, be that in our practical life and 
scientific work we must still continue to think of natural 
forces as efficient agents. But, if so, let us at least re- 
member that this attitude of mind must be regarded only 
as our ordinary work-clothes—necessary work-clothes it 
may be of our outer lower life—to be put aside when we 
return home to our inner higher life, religious and philo- 
sophical. 


CHAPTER IV. 
THE RELATION OF MAN TO NATURE. 


THERE are two widely distinct views concerning the 
relation of man to Nature ; the one as old as the history 
of human thought, the other only now urged upon us 
by modern science. According to the one, man is the 
counterpart and equivalent of Nature. He alone has— 
in fact is—an immortal spirit, and therefore he belongs 
to a world of hisown. According to the other, man is 
but a part, a very insignificant part of Nature, and con- 
nected in the closest way with all other parts, especially 
with the animal kingdom. He has no world of his own, 
nor even kingdom of his own: he belongs to the animal 
kingdom. In that kingdom he has no department of 
his own: he is a vertebrate. In the department of verte- 
brates he has no privileged class of his own: he is a 
mammal. In the class of mammals he has no titled 
order of his own: he is a primate, and shares his pri- 
macy with apes. It is doubtful if he may enjoy the pri- 
vacy of a family of his own—the Hominide—for the 
structural differences between man and the anthropoid 
apes are probably not so great as between the sheep 
family and the deer family. 


THE RELATION OF MAN TO NATURE. B05 


Now it is evident that these two are only views from 
different points, psychical and structural. From the 
psychical point of view it is simply impossible to exag- 
gerate the wideness of the gap that separates man from 
even the highest animals. From this point of view 
man must be set over as an equivalent, not only to the 
whole animal kingdom, but to the whole of N ature be- 
sides. From the structural point of view, on the con- 
trary, it is impossible to exaggerate the closeness of the 
connection. Man’s body is identified with all Nature in 
its chemical constituents, with the body of all animals 
in its functions, with all vertebrates, especially mammals, 
in its structure. Bone for bone, muscle for muscle, 
ganglion for ganglion, almost nerve-fiber for nerve-fiber, 
his body corresponds with that of the higher animals. 
Whether he was derived from lower animals or not, cer- 
tain it is that his structure even in the minutest details 
is precisely such as it would be if he were thus derived 
by successive slight modifications. 

Now, of these two views, the latter has been in recent 
times enormously productive in increasing our knowl- 
edge. Anatomy has become truly scientific only through 
comparative anatomy ; physiology through comparative 
physiology ; embryology through comparative embryol- 
ogy. Sociology is fast following in the same line, and 
becoming scientific through comparative sociology. Is 
not the same true also of psychology? Will not psy- 
chology become truly scientific only through comparative 
psychology, 1. e., by the study of the spirit of man in re- 


306 EVOLUTION AND RELIGIOUS THOUGHT. 


lation to what corresponds to it in lower animals? But 
this view and this method, when pushed to what seems 
to many their logical conclusion, end in identification of 
man with mere animals, of spirit with mere physical and 
chemical forces, immortality with mere conservation of 
energy, and thus leads to blank and universal materialism. 
Thus, while it increases our knowledge, it destroys our 
hopes. Isthereanyescape? There is. The twoextreme 
views given above are not irreconcilable. As already 
said, they are only views from different points, and there- 
fore, although both true, are equally one-sided and partial, 
and a true and rational philosophy, in this as in all other 
cases of vexed questions, is found only in a higher view, 
which combines and reconciles these mutually excluding 
extremes. Can we find such a view? I think we can. 

Let us first, however, trace some of the stages of this 
scientific materialism. ‘There are two main branches 
of the argument for materialism: one derived from 
brain-physiology, the other from evolution. As we wish 
to be perfectly fair, we will present and even press the 
argument in both these directions, although the latter 
alone bears directly on the subject in hand. 

In recent times, physiology has made great and, to 
many, startling advances in the direction of connecting 
mental phenomena with brain-changes. Physiologists 
have established the correlation of vital with chemical 
and physical forces,* and probably in some sense, at 


* See an article by the author on this subject, “American Journal of 


THE RELATION OF MAN TO NATURE, 307 


least, of mental with vital forces. They have proved, in 
every act of perception, first a physical change in a nerye- 
terminal, then a propagated thrill along a nerve-fiber, 
and then a resulting change, physical or chemical, in the 
brain; and in every act of volition, a change first in a 
brain-cell, then a return thrill along a nerve-fiber, and a 
resulting contraction of a muscle. ven the velocity of 
the transmission to and fro has been measured, and 
the time necessary to produce brain-changes estimated. 
They have also established the existence of physical and 
chemical changes in the brain corresponding to every 
change of mental state, and with great probability an 
exact quantitative relation between these changes of 
brain and the corresponding changes of mind. In the 
near future they may do more: they may localize all the 
different faculties and powers of the mind, each in its 
several place in the brain, and thus lay the foundations 
of a truly scientific phrenology. In the far-distant fu- | 
ture we may possibly do much more. We may connect 
each kind of mental state with a different and distinctive 
kind of brain-change. We may find, for example, a 
right-handed rotation of atoms associated with Jove, and 
a left-handed rotation associated with hate, or a gentle 
sideways oscillation associated with consciousness, and a 
vertical pounding associated with will. Now, suppose 
all this, and even much more, be done in the way of 
associating, both in degree and in kind, mental changes 


Science,” series ii, vol. xxviii, p. 305, 1859, and in “ Popular Science 
Monthly,” vol. iv, p. 156, 1873. 


308 EVOLUTION AND RELIGIOUS THOUGHT. 


with brain-changes. What then? ‘‘ Why,” say the ma- 
terialists, “‘ we thereby identify mind with matter, men- 
tal forces with material forces. Thought, emotion, con- 
sciousness and will become products of the brain, in the 
same sense as bile is a product of the liver, or ureaa 
product of the kidneys.” 

Such is, in brief, the argument. Now, the answer: 
We-may do all we have supposed and much more. We 
may push our knowledge in this direction as far as the 
boldest imagination can reach, and even then we are no 
nearer the solution of this mystery of the relation of 
brain-changes and mental changes than we are now. 
Even then it would be impossible for us to conceive how 
brain-changes produce mental changes or vice versa. 
Physical changes in sense-organs, transmitted along 
nerye-fibers, determine changes in brain-substance. So 
much is intelligible. But now there appear—how it is 
impossible to imagine—consciousness, thought, emotion, 
etc.—phenomena of an entirely different order, belong- 
ing to an entirely different world. So different, that it is 
impossible to imagine the nature of the nexus between, 
or to construe the one in terms of the other. Brain-cells 
are agitated and thought appears: Aladdin’s lamp is 
rubbed, and the genie appears. There is just as much 
intelligible causal relation between the two sets of phe- 
nomena in the one case as in the other. 

Now, this mystery is not of the nature of those which 
disappear under the light of knowledge. On the con- 
trary, sclence only brings it out in sharper relief, and 


THE RELATION OF MAN TO NATURE. = 309 


emphasizes its absolute unsolvableness. Suppose an ab- 
solutely perfect knowledge, perfect in degree, but human 
in kind. Suppose an ideally perfect science—a science 
which has so completely subdued its domain, and re- 
duced it to such perfect simplicity, that the whole cos- 
mos may be expressed in a single mathematical formula 
—a formula which, worked out with plus signs, would 
give every phenomenon and event which shall ever occur 
in the future, and with minus signs every phenomenon 
and event which has ever occurred in the past. Surely, 
this is an ideally perfect science. Yet, even to such a 
science, the relation of brain-changes to mental states 
would be as great a mystery as now. It would even 
come out in stronger relief, because so many other ap- 
parent mysteries would disappear. Like the essential 
nature of matter or the ultimate cause of force, this rela- 
tion lies evidently beyond the domain of science. It re- 
quires some other kind of knowledge than human to 
understand it. 

But materialists insist so much on the identity of 
brain-physiology with psychology, that even at the risk 
of tediousness we will multiply illustrations in order, if 
possible, to make this point still clearer. Suppose, then, 
we exposed the brain of a living man in a state of intense 
activity. Suppose, further, that our senses were abso- 
lutely perfect, so that we could see every change, of 
whatever sort, taking place in the brain-substance. 
What would we see? Obviously nothing but molecular 
changes, physical and chemical; for to the outside ob- 


810 EVOLUTION AND RELIGIOUS THOUGHT. 


server there is absolutely nothing else there to see. But 
the subject of this experiment sees nothing of all this. 
His experiences are of a different order, viz., consciousness, 
thought, emotions, etc. Viewed from the outside, there is 
—there can be—nothing but motions; viewed from the 
inside, nothing but thought, etc.—from the one side, only 
‘physical phenomena; from the other side, only psychical 
phenomena. Is it not plain that, from the very nature of 
the case, it must ever be so? Certain vibrations of brain 
molecules, certain oxidations with the formation of car- 
bonic acid, water, and urea on the one side, and there 
appear on the other sensations, consciousness, thoughts, 
desires, volitions. There are, as it were, two sheets of 
blotting-paper pasted together. The one is the brain, 
the other the mind. Certain ink-seratches or blotches, 
utterly meaningless on the one, soak through and appear 
on the other as intelligible writing, but how we know 
not, and can never hope to guess. But when “the paste 
dissolves, shall the writing remain? We shall see. 
But some will object. There is nothing specially 
strange and unique in all this, for the same mystery un- 
derlies the essential nature of all kinds of force and 
matter, and therefore all phenomena. ‘True enough, 
but with this difference. Physical and chemical forces 
and phenomena are indeed incomprehensible in their es- 
sential nature; but once accept their existence, and all 
their different forms are mutually convertible, construa- 
ble in terms of each other and all in terms of motion. 
But it is impossible by any stretch of the imagination 


THE RELATION OF MAN TO NATURE. 311 


to thus construe mental forces and mental phenomena. 
It may, indeed, be impossible to conceive how came the 
plane of material existence, but, standing on that plane, 
all phenomena fall into intelligible order. But there 
is another plane above this one, having no intelligible 
relation with it. We must climb up and stand on this 
before its phenomena fall into intelligible order. In, 
a word, material forces and phenomena are, indeed, a 
mystery, but only of the first order. But mental and 
moral forces and phenomena are a mystery even from the 
standpoint of the other, and are therefore a mystery of 
the second order—a mystery within a mystery. 

We repeat, then, with additional emphasis after this 
examination, that we can not imagine between physical 
and psychical phenomena a relation of cause and effect 
in the same sense in which we use these terms in physi- 
cal science, although in some sense there is doubtless 
such a relation. If man were the only animal we had 
to deal with, there would be no standing ground left for 
materialism. But there is still another difficulty which 
sticks deeper. It is that suggested by the law of evolu- 
tion and enforced by the comparative method. 

Relation of Man to Animals.—Man, we say, is en- 
dowed with, zs, in fact, an immortal spirit. What is 
spirit? We know things only by their phenomena ; 
what are the phenomena of spirit ? Consciousness, will, 
intelligence, memory, love, hate, fear, desire —surely 
these are some of them. But has not a dog or a monkey 
all these ? Pressed with this difficulty, some have in- 


319 EVOLUTION AND RELIGIOUS THOUGHT. 


deed felt compelled to accord immortal spirit to higher 
animals. But we can not stop here. If to these, then 
also to all animals ; for we have here only a sliding scale 
without break. Can we stop now and make it coexten- 
sive with sentiency ? No; for the lowest animals and 
lowest plants merge into each other so completely that 
no one can draw the line between them with certainty. 
We must extend it to plants also. Shall we stop here 
and make immortal spirit coextensive with life? We 
can not ; for life-force is certainly correlated with, trans- 
mutable into, and derivable from, physical and chemical 
forces. We must extend it into dead nature also, 
Therefore, everything is immortal or none. Our boasted 
immortality by continued extension becomes thinner and 
thinner until it evaporates into thin air. It becomes 
naught else than conservation of energy, and not, as we 
had hoped, conservation of self-conscious personality. 
This may be interesting as a scientific fact; but of what 
value to us personally is a continued existence of our 
spiritual forces as heat, light, electricity, or any other 
form of unconscious force? ‘Thus, then, if once we pass 
the gap between man and the higher animals, there is no 
possibility of a stopping-place anywhere. 

Such is the difficulty presented by comparison in the 
taxonomic series. ‘Take now the embryonic series. Each 
one of us, individually, was formed gradually by a pro- 
cess of evolution, from a microscopic spherule of proto- 
plasm undistinguishable in structure from the lowest 
forms of protozoal life. Now, in this gradual process of 


THE RELATION OF MAN TO NATURE. 313 


evolution, where did immortal spirit come in? Was 
it in the germ-cell? Then why deny it to the proto- 
zoan? Was it at the quickening, or at the birth, or at 
the moment of first self-consciousness, or at some later 
period of capacity of abstract thought? Again, when 
it did come in, was it something superadded or did it 
grow out of something already existing in the embryo 
or the infant? 

Or take the evolution series from protozoan to man. 
This we have already seen is similar in outline to the 
other two. Now, in the gradual evolution of the animal 
kingdom throughout all geological time, terminating in 
man, when did immortal spirit come in? Did it enter 
with life, or with sentient life, or somewhere in the 
ascending scale of animals, or with the advent of man ? 
_If with man, was it some new thing added at once out 
of hand, or did it grow out of something already exist- 
ing in animals ? 

This last, we are persuaded, is the only tenable view— 
the only view that can effect that reconciliation between 
the two extreme, mutually excluding views now usually 
held, which, as already seen, is the true test of a rational 
philosophy. I believe that the spirit of man was devel- 
oped out of the anima or conscious principle of animals, 
and that this, again, was developed out of the lower forms 
of life-force, and this in its turn out of the chemical and 
physical forces of Nature ; and that at a certain stage in 
this gradual development, viz., with man, it acquired the 
property of immortality precizely as it now, in the indi- 


814 EVOLUTION AND RELIGIOUS THOUGHT. 


vidual history of each man at a certain stage, acquires 
the capacity of abstract thought. This is, in brief, the 
view which I wish to enforce. The reader must under- 
stand, however, that this is my own view only, a view for 
which I have earnestly contended for twenty years. It 
appeals, therefore, not to authority, but only to reason. 
I wish now to present it as briefly as possible. 

First, then, I would draw attention to the fact that 
there is nothing wholly exceptional in such transforma- 
tion with the sudden appearance of new powers and 
properties ; but, on the contrary, it is in accordance with 
many analogies in the lower forces, and therefore a 
priort not only credible but probable. For example, 
force and matter may be said to exist mow on several 
distinct planes raised one above another. ‘There is a sort 
of taxonomic scale of force and matter. ‘These are, 1, 
the plane of elements; 2, the plane of chemical com- 
pounds; 3, the plane of vegetal life; 4, the plane of 
animal life ; and 5, the plane of rational and, as we hope, 
immortal life. Each plane has its own appropriate force 
and distinctive phenomena. On the first operates physi- 
cal forces, producing physical phenomena only —for 
the operation of chemical affinity immediately raises mat- 
ter to the next plane. On the second plane operates, in 
addition to physical, also chemical forces, producing all 
those changes by action and reaction, the study of which 
constitutes the science of chemistry. On the third plane, 
in addition to the two preceding forces, with their char- 
acteristic phenomena, operates also life-force, produc- 


THE RELATION OF MAN TO NATURE. 315 


ing the distinctive phenomena characteristic of living 
things. On the fourth plane, in addition to all lower 
forces and their phenomena, operates also a higher form 
of life-force characteristic of animals, producing the phe- 
nomena characteristic of sentient life, such as sensation, 
consciousness, and will. On the fifth plane, in addition 
to all the preceding forces and phenomena, we have also 
the forces and phenomena characteristic of rational and 
moral life. 

Now, although there are doubtless great differences of 
level on each of these planes, yet there is a very distinct 
break between each. Although there are various degrees 
of the force characteristic of each, yet the difference be- 
tween the characteristic forces is one of kind as well as of 
degree. Although energy by transmutation may take all 
these different forms, and thus does now circulate up and 
down through all these planes, yet the passage from one 
plane upward to another is not a gradual passage by slid- 
ing scale, but at one bound. When the necessary condi- 
tions are present, a new and higher form of force at once 
appears, like a birth into a higher sphere. For example, 
when hydrogen and oxygen are brought together under 
proper conditions, water is born—a new thing with new 
and wholly unexpected properties and powers, entirely 
different from those of its components. When CO,, H,0, 
and NH, are brought together under suitable conditions, 
viz., in the green leaves of plants, in the presence of sun- 
light, living protoplasm is then and there born, a some- 
thing yang entirely new and unexpected powers and 


316 EVOLUTION AND RELIGIOUS THOUGHT. 


properties. It is no gradual process but sudden, like birth 
into a higher sphere. 

Now, there is not the least doubt that the same is true 
of the order and manner of the first appearance of the 
natural forces in the phylogenic series. In the history of 
the evolution of the cosmos, the forces of Nature have 
appeared successively and suddenly when conditions be- 
came favorable. There was a time in the history of the 
earth when only physical forces existed, chemical affinity 
being held in abeyance by the intensity of the heat.* By 
gradual cooling, chemical affinity at a certain stage came 
into being—was born, a new form of force, with new and 
peculiar phenomena, though doubtless derived from the 
preceding. Ages upon ages passed away until the time 
was ripe and conditions were favorable, and life appeared 
—a new and higher form of force, producing a still more 
peculiar group of phenomena, but still, as I believe, de- 
rived from the preceding. Ages upon ages again passed 
away, during which this life-force took on higher and _ 
higher forms—in the highest foreshadowing and simu- 
lating reason itself—until finally, when the time was 
fully ripe and conditions were exceptionally favorable, 
spirit, self-conscious, self-determining, rational, and mor- 
al, appeared—a new and still higher form of force, but 
still, as I am persuaded, derived from the preceding. 

Now, that these forces are really of derivative origin is 
proved by the fact that we see every step of this process 


* All chemical compounds are dissociated by sufficient heat, 


THE RELATION OF MAN TO NATURE. 817 


taking place daily under our very eyes. I pass over the 
conversion of physical into chemical force because this is 
admitted on all hands. I begin, therefore, with vital 
force. Sunlight falling on green leaves disappears as light 
and reappears as life—is consumed in doing the work of 
decomposing CO,, H,O, and NH,, and the C, H, O, and 
N thus set free from previous combination unite to form 
living protoplasm.* Again, in the embryonic history of 
every animal we see the next change take place—i. e., the 
emergence of the psychic out of the vital. In the germ- 
cell, in the egg, and even in the early stages of the em- 
bryo, there is no distinctive animal life—i. e., no con- 
sciousness, nor volition, nor response of any kind to 
stimulus. At a certain stage distinctive animal or psy- 
chic life appears. We call it quickening. Materials for 
psychology are now present for the first time. In man 
alone, and that only some time after physical birth, we 
see the last change. The new-born child has animal life 
only. The emergence of self-consciousness—a change so 
wonderful that it may well be called the birth of spirit— 
takes place only at the age of two to three years. Now 
for the first time we have phenomena distinctive of hu- 
manity. 

But some will ask, “ How is this consistent with im- 
mortality?” In answer, let me again remind the reader 


—_—_———_ 


* The origin of vital from chemical force in the grecn leaves of 
plants can not be doubted; but this does not, of course, explain the 
mystery of the first origin of life on the earth, for one condition of the 
change now is the contact of living matter, 


818 EVOLUTION AND RELIGIOUS THOUGHT. 


that with every new form of force, with every new birth 
of the universal energy into a higher plane, there appear 
new, unexpected, and, previous to experience, wholly un- 
imaginable properties and powers. This last birth is of 
course no exception. Why may not immortality be one 
of these new properties? But this point is so important 
that we must treat it more fully. 

Remember, then, the view of the relation of God to 
Nature, already explained. Remember that the forces of 
Nature are naught else than different forms of the one 
omnipresent Divine energy. Remember that, as just 
shown, this Divine omnipresent energy has taken on suc- 
cessively higher and higher forms in the course of cosmic 
time. Now this upward movement has been wholly by 
increasing individuation, not only of matter, but also 
of force. This universal Divine energy, in a generalized 
condition, wnindividuated, diffused, pervading all Na- 
ture,.is what we call physical and chemical force. The 
same energy in higher form, individuating matter, and | 
itself individuated, but only yet very imperfectly, is what 
we call the life-force * of plants. The same energy, more 


* T know it is the fashion to ridicule the use of the terms vitality, 
vital force, as a remnant of an old superstition; and yet the same men 
who do so use the terms gravity, electricity, chemical force, ete. Vital 
force is indeed corvelated with other forces of Nature, but is none the 
less a distinct form of force, far more distinct than any other unless it 
be the still higher form of psychical, and therefore it better deserves a 
distinct name than any lower form. Each form of force gives rise to a 
peculiar group of phenomena, and the study of these to a special depart- 
ment of science. Now, the group of phenomena called vital is more 
peculiar, more different from other groups than these are from each 


THE RELATION OF MAN TO NATURE. 319 


fully individuating matter and itself more fully individu- 
ated, but not completely, we call the anima of animals. 
This anima, or animal soul, as time went on, was indi- 
viduated more and more until it resembled and foreshad- 
owed the spirit of man. Finally, still the same energy, 
completely individuated as a separate entity and therefore 
self-conscious, capable of separate existence and therefore 
immortal, we call the spirit of man. 

According to this view, the vital principle of plants 
and the anima of animals are but different stages of the 
development of spirit in the womb of Nature: in man at 
last it came to birth. In plants and animals it was in 
deep embryo sleep—in the latter, quickened, indeed, but 
not viable—still unconscious of self, incapable of inde- 
pendent life, with physical, umbilical connection with 
Nature; but now at last in man, separated from Nature, 
capable of independent life, born into a new and higher 
plane of existence. Separated, but not wholly: Nature is 
no longer gestative mother, but still newrsing mother of 
spirit. As the organic embryo at birth reaches independ- 
ent material or temporal life, even so spirit embryo by 
birth attains independent spiritual or eternal life. 

Although birth is its truest correspondence and best 
illustration, yet we may vary the illustration in many 
ways: 


other, and the science of physiology is a more distinct department than 
either physics or chemistry, and therefore the form of force, which de- 
termines these phenomena, is more distinct and better entitled to a name 
than any physical or chemical force. 


320 EVOLUTION AND RELIGIOUS THOUGHT. 


1. Nature may be likened to a level water-surface. 
This represents unindividuated physical and chemical 
force. On this surface some individuating force pulls up 
a portion of the water into a commencing drop. This 
represents the condition of spirit in plants. Or by greater 
force the surface may be lifted higher into a nipple-like 
eminence simulating a drop, or even into an almost com- 
plete drop, with only a neck-like connection with the 
general surface. ‘This represents the condition of spirits 
in the higher animals. In all these cases, even though 
the drop be nearly completed, if we remove the individu- 
ating or lifting force, the commencing drop is immedi- 
ately drawn back by cohesion and refunded into the 
general watery surface. But, once complete the drop, and 
there is no longer any tendency to revert, even though the 
lifting force is removed. This represents the condition 
of spirit in man. 

2. Or Nature may, again, be likened to a water-surface 
beneath which the anima of animals is deeply and tran- 
quilly submerged, wholly unknowing of any higher, freer 
world above. In man spirit emerges above the surface 
into a higher world, looks down on Nature beneath him, 
around on other emerged spirits about him, and up- 
ward to the Father of all spirits above him. Emerged, 
but not wholly free—head above, but not yet foot-loose. 

3. Or, again: As a planet must break away from 
physical, cohesive connection with the central sun (planet- 
birth) in order to enter into higher gravitative relations, 
which thenceforward determine all its movements in 


THE RELATION OF MAN TO NATURE. 321 


beautiful harmony ; as the embryo must break away from 
physical umbilical connection with the mother in order 
to enter into higher spiritual bonds of love, which 
thenceforward determine all their mutual relations—even 
so spirit must break away from physical and material 
connection with the forces of Nature, which are but the 
omnipresent Divine energy, in order thereby to enter 
into higher relations of filial love to God and brotherly 
love to man. 

4, As the new-born child differs little in grade of 
physical organization from the mature but unborn em- 
bryo, but at the moment of birth there is a sudden and 
complete change, not so much in the grade of organiza- 
tion but in the whole plane of existence—a change abso- 
lutely necessary for further advance, for another cycle of 
life; even so at the moment of the origin of man, howso- 
ever this may have been accomplished, there may have 
been no great change in the grade of psychical structure, 
but yet a complete change in the plane of psychical life 
—a change absolutely necessary for further advance, for 
another cycle of evolution. In both cases there is a sud- 
den entrance into a new world, the sudden appearance of 
a new creature with entirely different capacities—a pass- 
ing out of an old world, a waking up in a new and 
higher. According to this view, man alone is a child of 
God, capable of separate spirit-life—separate but not yet 
wholly independent of Nature. As already said, Nature 
is no longer gestative mother, but still nursing mother of 
spirit—we are weaned only by death. 


322 EVOLUTION AND RELIGIOUS THOUGHT. 


5. Or, again: As in passing up the organic scale, we 
find all grades of completeness of organic individuality, 
an increasing individuation of bodily form which com- 
pletes itself as a perfect organic individual only in the 
higher animals, so, also, in passing up the dynamic scale, 
force or energy is individuated more and more until 
the process reaches completeness as a spirit-individual or 
dynamic individual—a person only in man. Organic 
individuality completes itself in animals. Psychic indi- 
viduality only in man. 

6. One more illustration and the last. The animal 
body may be likened to an exquisitely adjusted instru- 
ment of communication between two worlds—the ma- 
terial world without and the spiritual world within. 
The key-boards of this marvelous instrument are the 
nerve-terminals of the sense-organs in contact with the 
material world, and the brain-cells in touch with the 
spirit-world. External Nature plays on the one by 
sensation and determines changes in spirit. Spirit plays 
on the other by will and muscular contraction, and de- 
termines changes in external Nature. Now, in animals 
spirit is fast asleep or at most dreaming, or even perhaps 
somnambulistic, but at least unconscious of self, and acts 
only by stimulus—only responds in some sense automat- 
ically as sleepers do. In man spirit is wide awake and 
may respond automatically like animals, or may choose 
not to respond at all. Moreover, it acts freely in its own 
domain—the world of ideas—without external stimulus ; 
or of its own free-will may initiate changes in the ex- 


THE RELATION OF MAN TO NATURE. 323 


ternal world. With God all phenomena commence at 
the spirit-end. In animals all commence at the matter- 
end, and by automatic response terminate in the same. 
Man alone lives in both worlds, partakes of both natures, 
and acts according to either method. 

~The more we reflect on this subject, the more we 
shall be convinced that completed spirit individuality 
explains, as nothing else can, all that is characteristic 
of man. It is this which constitutes person, or the 
self-acting ego. It is this which constitutes self-con- 
sciousness, free-will, and moral responsibility. And out 
of these, again, grows, the recognition of relations to 
other moral beings and to God, and therefore ethics and 
religion. Out of these, also, grows the capacity of indefi- 
nite voluntary progress. This also means separate life, 
spirit-viability, or immortality. Self-consciousness espe- 
cially seems to me the simplest sign of separate entity or 
spirit-individuality, and its appearance among psychical 
phenomena the very act of spirit-birth. We may im- 
agine man to have emerged ever so gradually from 
animals: in this gradual development the moment he 
became conscious of self, the moment he turned his 
thoughts inward in wonder upon himself and on the 
mystery of his existence as separate from Nature, that 
moment marks the birth of humanity out of animality. 
All else characteristic of man followed as a necessary 
consequence. I am quite sure that, if any animal, say a 
dog or a monkey, could be educated up to the point of 
self-consciousness (which, however, I am sure is impos- 


394. EVOLUTION AND RELIGIOUS TOOUGHT. 


sible), that moment he (no longer 77) would become a 
moral responsible being, and all else characteristic of 
moral beings would follow. At that moment would 
come personality, immortality, capacity of voluntary 
progress ; and science, philosophy, religion, would quick- 
ly follow. | 

We have emphasized self-consciousness as the most 
fundamental sign of spirit-individuality; but a difference 
of exactly the same kind is found running through the 
whole gamut of human faculties as compared with corre- 
sponding faculties in animals. As animal consciousness 
is related to human self-consciousness, so exactly is ani- 
mal will to human free-will, animal intelligence to hu- 
man reason, animal sign-language to rational grammati- 
cal speech of man, constructive art of animals to true ra- 
tional progressive art of man. In every one of these the 
resemblance is great, but the difference is immense, and 
not only in degree but also in kind. In every case it is 
like shadow and substance, promise and fulfillment, or, 
still better, it is like embryo and child. The change 
from one to the other is like to a birth into a higher 
sphere, the beginning of another cycle of evolution. We 
would like to follow this idea out in detail, but it would 
lead us beyond the scope of this work. Those who desire 
to do so we would refer to an article by the author on the 
“ Psychical Relation of Man to Animals.” * 

But it will be objected that there are other births 





* “ Princeton Review” for May, 1884. 


THE RELATION OF MAN TO NATURE. 325 


of energy from lower to higher condition; but such 
births do not insure continued existence in the higher 
condition. In the gradual evolution of energy described 
on page 316, when a portion rises from physical to 
chemical, from chemical to vital, or from vital to sen- 
tient, it does not remain ever after in the higher con. 
dition—there is no immortality on the higher plane, 
On the contrary, all these lower forms of energy are 
continually ascending and descending; transformation 
is downward as well as upward. Why should there be 
an exception in this last birth? In these successive 
upward metamorphoses of energy why should the last 
only be permanent? I answer: Because it reaches at 
last its final goal, viz., complete individuation, as free, 
self-acting spirit; it reaches again the spiritual plana 
from which it sprang, and becomes thereby a partaker 
of the Divine nature; because it comes at last into moral 
relations with the absolute—the Divine—and thereforo 
above the plane of shifting changes. If the scale of 
energy be likened to a ladder with many rounds, reaching 
from the plane of matter to the plane of spirit, then so 
long as energy is on the ladder it ascends and descends ; 
but, once it reaches the plane of free spirit, it is in a 
wholly new world in which eternal ascent is the law. 

Perhaps I can best bring out the reasonableness of 
my view by comparing it with other possible alternative 
views. 

There are three possible views as to the nature, the 
origin, and the destiny of the human spirit: (1.) That it 


326 EVOLUTION AND RELIGIOUS THOUGHT. 


pre-existed always—uncreated, underived, eternal, both 
ways—backward as well as forward. Therefore, as it 
never began, so it will never end. It is ¢mmortal of its 
own right. ‘This is substantially the view of Plato, of 
Leibnitz, and perhaps some other philosophers.  (2.) 
That it is derived from God directly—created at once 
without natural process ; that at the moment of creation 
of the first man Adam, and at some unknown time and 
in some inscrutable way in the history of each individ- 
ual, it was injected into the body from the outside, and 
at the same time endowed with immortality. This, I 
take it, is the orthodox view. (3.) That it was indeed 
derived from God, but not directly; created indeed, but 
only by natural process of evolution; that it indeed pre- 
existed, but only as embryo in the womb of Nature, 
slowly developing through all geological times, and finally 
coming to birth as diving soulin man. Thus it attains 
immortality at a certain stage of development, viz., at 
spirit-birth. This is the view I have striven to enforce. 
I hold up these three views: Which is the more 
rational? The view of Plato—that of self-existent, un- 
— ereated, eternal spirit—I think few will entertain at this 
time of the world’s day. The usual orthodox view I 
have shown is surrounded with insuperable difficulties ; 
is wholly unscientific and irrational. What is there left 
but the view presented above? Plato is right in asserting 
pre-existence, but wrong in denying creation. The usual 
view is right in asserting creation, but wrong in denying 
natural process. The view I have presented asserts pre- 


THE RELATION OF MAN TO NATURE. 327 


existence in embryo and creation by natural process. It 
therefore combines and reconciles the two extreme views, 
and is more rational than either. 

Some General Conclusions.—There are still two or 
three thoughts so closely connected with what we have 
already said that we can not pass them over: 

1. We have seen that every mental state corresponds 
with a particular brain state, and every mental change 
with a brain change. We have, therefore, here, two 
series, physical and psychical, corresponding with each 
other, term for term. For every change in the one there 
is a corresponding change in the other, both in kind and 
amount. Now, is not this the test of the relation of 
cause and effect? It certainly is. Yes, there must be 
a causal relation here, even though we are not able to 
understand the nature of the causal nexus. But which 
is cause and which effect? If the view above presented 
be correct, then in animals drain changes are in all cases 
the cause of psychical phenomena. In man alone, and 
only in his higher activities, psychic changes precede 
and determines brain changes. In man alone brain 
changes are determined not only by external but by 
internal impressions. Man alone perceives not only ob- 
jects—material things—but also relations and properties 
abstracted from the objects, 1. e, tdeal things; and, 
moreover, not only relations between objects, but also 
relations between relations or ideas. In man alone 
there is an inner world —microcosm—the things of 
which are thoughts, ideas, etc. This self-acting power 


828 EVOLUTION AND RELIGIOUS THOUGHT. 


of spirit on the things of itself, instead of merely re- 
acting as played upon by external nature, is charac- 
teristic of man, and is a necessary result and a sign 
of severance, partial at least, of physical bond with 
Nature. 

2. Again, I have used the term vital principle. I 
must justify it. I know full well that it is the fashion 
to ridicule the term as a remnant of an old superstition 
which regards vital force as a sort of supernatural entity 
unrelated to other forces of Nature. No one has striven 
more earnestly than myself to establish the correlation of 
vital with physical and chemical forces;* and yet, if the 
view above presented be true, there is a kind of justifica- 
tion even for the term vital principle—much more, vital 
force. There is a kind of reason and true insight in the 
personification of the forces of Nature, and especially of 
vital force. All forces, by progressive dynamic indi- 
viduation, are on the way toward entity or personality, but 
fully attain that condition only in man. 

3. Again, to perceive relations and properties ab- 
stracted from material things, to form abstract or general 
ideas, to form not only percepts but also concepts, is ad- 
mitted to be a characteristic of man—a characteristic on 
which all our science and philosophy rest. From time 
immemorial the vexed question has been debated, “* Have 
such abstract or general ideas any real existence, or are 
they mere names of figments of the mind?” This is 
the famous question of realism and nominalism. Now, 


* “ Popular Science Monthly,” December, 1873. 


THE RELATION OF MAN TO NATURE. 329 


if our view be correct, then there is one most funda- 
mental abstraction, viz., self, which is indeed a reality. 
Self-consciousness is the direct recognition of the one 
reality, spirit, of which all others are the sign and 
shadow—the true reality which underlies and gives po- 
tency to all abstractions or ideas. Do we not find in this 
view, then, the foundation of a true realism, or rather a 
complete reconciliation of realism and nominalism ? 

4, Thus, then, Nature, through the whole geological 
history of the earth, was gestative mother of spirit, 
which, after its long embryonic development, came to 
birth and independent life and immortality in man. Is 
there any conceivable meaning in Nature without this 
consummation? All evolution has its beginning, its 
course, its end. Without spirit-immortality this beauti- 
ful cosmos, which has been developing into increasing 
beauty for so many millions of years, when its evolution 
has run its course and all is over, would be precisely as if 
it had never been—an idle dream, an idiot tale signifying 
nothing. I repeat: Without spirit-immortality the cos- 
mos has no meaning. Now mark: It is equally evident 
that, without this gestative method of creation of spirit, 
the whole geological history of the earth previous to man 
would have no meaning. If man’s spirit were made at 
once out of hand, why all this elaborate preparation by 
evolution of the organic kingdom? The whole evolution 
of the cosmos through infinite time is a gestative process 
for the birth of spirit—a divine method of the creation of 
spirits. 


330 EVOLUTION AND RELIGIOUS THOUGHT. 


Thus, again, man is born of Nature into a higher na- 
ture. He therefore alone is possessed of two natures—a 
lower, in common with animals, and a higher, peculiar 
to himself. The whole mission and life-work of man is 
the progressive and finally the complete dominance, both 
in the individual and in the race, of the higher over the 
lower. The whole meaning of sin is the humiliating 
bondage of the higher to the lower. As the material 
evolution of Nature found its goal, its completion, and 
its significance in man, so must man enter immediately 
upon a higher spiritwal evolution to find its goal and 
completion and its significance in the ideal man—the 
Divine man. As spirit, unconscious in the womb of Na- 
ture, continued to develop by necessary law until it came 
to birth and independent hfe in man, so the new-born 
spirit of man, both in the individual and in the race, 
must ever strive by freer law to attain, through a newer 
birth, unto a higher life. 


CHAPTER V. 
THE RELATION OF GOD TO MAN. 


In the two preceding chapters we have discussed the 
relation of God to Nature and of man to Nature. There 
is still another relation, if possible, of still more vital im- 
portance to us, viz., the relation of God to man. This, 
of course, introduces the question of revelation—a sub- 
ject which I approach with some reluctance. I feel I am 
treading on holy ground, and must do so with shoes re- 
moved. If it be asked, How is evolution concerned 
with the subject of revelation? I answer Evolution 
emphasizes and enforces the reign of law taught by all 
science, and makes it at last wniversal. Many conclude, 
therefore, that, if evolution be true, a belief in the possi- 
bility of any form of revelation is irrational. I do not 
think this follows, and I will give my reasons. I do so, 
however, very briefly, because we are not yet ready to 
formulate our views except in the most general way. 

If man be indeed something more than a higher spe- 
cies of animal ; if man’s spirit be indeed a spark of Di- 
vine energy individuated to the point of self-conscious- 
ness and Ea Sat of his relation to God ; if spirit- 


832 EVOLUTION AND RELIGIOUS THOUGHT. 


embryo, developing in the womb of Nature through all 
geological time, came to birth and independent spirit-life 
in man, and thus man alone is a child of God as well as a 
product of Nature—if all this be true, then it is evident 
that this wholly new relation requires also a wholly differ- 
ent mode of Divine operation. If God operates on 
Nature only by regular processes, which we call natural 
laws, then he must operate on spirit in a different and 
a more direct way, and this we call revelation. If to the 
student of Nature it is inconceivable that He should 
operate on Nature except by natural laws (for this 
is the name we give to His chosen mode of operation 
there), then to the student of theology it is equally incon- 
ceivable, if our view of man be true, that He should not 
operate on spirit in some more direct and higher way, 
1. e., by revelation. 

But some will ask, Is not this a palpable violation of 
law ? I think not. All divine operations are, must be, — 
according to reason, i. e., according to law. ‘The opera- 
tion of the divine on the human spirit, i. e., revelation, 
must therefore be according to law, but a higher law 
than that which governs Nature, and, therefore, from the 
point of view of Nature, supernatural. ‘There is nothing 
wholly unique in this. Life is a higher form of force 
than the physical and chemical. Life-phenomena are 
therefore super-physical, and if we confined the term 
Nature to dead Nature they would be supernatural. So 
the free, self-determined acts of spirit on spirit, even of 
the spirit of man on the spirit of man, much more of the 


THE RELATION OF GOD TO MAN. 330 


Spirit of God on the spirit of man, may be according 
to law, and yet from the natural point of view be super- 
natural. It is true that, in the complex of phenomena, 
material and spiritual inextricably woven together, 
which go to make up human life, Science must ever 
strive to reduce as much as possible to material laws, for 
this is her domain, and she is bound to extend it; but, if 
our view of man be true, there will always remain a 
large residuum of phenomena—a whole world of phe- 
nomena—which will never yield, because clearly beyond 
her domain. Standing on the lower material plane, these 
phenomena are wholly super-material, and therefore in- 
comprehensible from the material point of view. We 
must rise and stand on the higher plane before these also 
are reduced to law, but a higher law than that operating 
on the lower plane. If, therefore, science insists on ban- 
ishing the supernatural from the realm of Nature, the- 
ology may reasonably insist on its necessity, im this sense, 
in the realm of morals and religion. 

If, then, the direct influence of the Spirit of God 
on the spirit of man be what we call revelation, then 
there is evidently no other kind of revelation possible ; 
and, furthermore, such revelation is given to all men in 
different degrees. It is given to all men as conscience ; 
in greater measure to all great and good men as clearer 
perception of righteousness ; in pre-eminent measure to 
Hebrew prophets and Christian apostles; but supremely 
and perfectly to Jesus alone. But there is, and in the 
nature of things there can be, no test of truth but rea- 


334 EVOLUTION AND RELIGIOUS THOUGHT. 


son. We must fearlessly, but honestly and reverently, 
try all things, even revelations, by this test. We must 
not regard, as so many do, the spirit of man as the pass- 
ive amanuensis of the Spirit of God. ‘Revelations to man 
must of necessity partake of the imperfections of the 
medium through which it comes. As pure water from 
heaven, falling upon and filtering through earth, must 
gather impurities in its course differing in amount and 
kind according to the earth, even so the pure divine 
truth, filtering through man’s mind, must take imperfec- 
tions characteristic of the man and of the age. Such fil- 
trate must be redistilled in the alembic of reason to 
separate the divine truth from the earthy impurities, 


CHAPTER VI. 


THE OBJECTION, THAT THE ABOVE VIEW IMPLIES PAN- 
THEISM, ANSWERED. 


It will be observed that the views presented in the 
last three chapters are closely connected with one another, 
and all conditioned on the ‘‘ Relation of God to Nature,” 
urged in Chapter III. Now it will doubtless be objected 
to this view, especially as applied in Chapter IV on the 
** Relation of Man to Nature,” that it is naught else than 
pure pantheism ; that it destroys completely the personal- 
ity of Deity, and with it all our hopes of communion 
with him, and all our aspirations of love and worship 
toward him ; that, according to this view, God becomes 
only the soul or animating principle of Nature, operat- 
ing everywhere but unconsciously like the vital principle 
of an organism ; that the whole cosmos becomes in fact a 
great organism, developing under the operation of resi- 
dent force according to necessary law, only that we 
apotheosize this omnipresent force and call it God ; and 
finally, that God is naught else than an abstraction, 
created like other abstractions or general ideas wholly by 
the human mind, and having no objective existence. 


336 EVOLUTION AND RELIGIOUS THOUGHT. 


Furthermore, it will be said, that according to this view, 
this omnipresent unconscious energy individuates itself 
by necessary law of evolution more and more until it 
reaches, for the first time in man, self-consciousness and 
immortality, and thus that man himself is the only self- 
conscious immortal being in existence, and therefore the 
only being worthy of reverence and worship. Thus, this 
view leads to humanity-worship or rather to self-worship. 

I feel the full force of this objection. I answer it as 
follows: I freely admit that, following up this scientific 
line of thought alone, we are carried strongly in the direc- 
tion of pantheism. But there is nothing strange or ex- 
ceptional in this. In all the deepest questions, single 
lines of thought inevitably carry us to extreme one-sided 
views. ‘This seems to be the necessary result of the 
essentially two-fold nature of man, self-conscious spirit 
in a material body, the relation between which is, and 
must ever be, inscrutable. On this account there is and 
must be a fundamental antithesis in human philosophy, 
i.e., two lines of thought, the material and spiritual, which 
lead to two apparently irreconcilable views.* We have 
already seen that a rational philosophy, whenever we are 
able to reach such, is always found in a higher and more 
comprehensive view, which includes, combines, and ree- 
onciles two one-sided, partial, and mutually excluding 
views. But spirit and matter, or mind and brain, or God 


* For a fuller statement of this antithesis, see an article by the author 
entitled “Evolution in Relation to Materialism,” “ Princeton Review,” 
for March, 1881. 


OBJECTION ANSWERED. 337 


and Nature, is the fundamental antithesis which underlies 
and is the cause of all other lesser antitheses. This anti- 
thesis, therefore, is absolutely fundamental, and therefore 
forever irreconcilable. We must accept both sides, even 
though we can not clearly perceive the nature of their 
relation. We must be content with compromise where 
we can not effect complete reconciliation. We must 
frankly acknowledge that the antagonism is apparent 
only, and the result of the limitation of our faculties, 
and believe that, if we could only rise to a high enough 
point of view, like all other antitheses, this also would 
disappear in a rational philosophy. 

Now, to apply these principles. No one, we admit, 
can form a clear conception of how immanence of Deity 
is consistent with personality, and yet we must accept 
both, because we are irresistibly led to each of these by 
different lines of thought. Science, following one line of 
thought, uncorrected by a wider philosophy, is naturally 
led toward the one extreme of pantheistic immanence; the 
devout worshiper, following the wants of his religious na- 
ture, is naturally led toward the other extreme of anthro- 
pomorphic personality. The only rational view is to 
accept both immanence and personality, even though we 
can not clearly reconcile them, i. e., immanence without 
pantheism, and personality without anthropomorphism. 
We have already seen in the third chapter, how follow- 
ing the scientific line of thought, we are logically driven 
to immanence. We wish now to show how, following an- 
other line of thought, we are as logically driven to per- 


888 EVOLUTION AND RELIGIOUS THOUGHT. 


sonality. On this most difficult subject, however, all we 
are prepared to do is to throw out some brief suggestions, 
in the hope that they may be carried out more perfectly by 
some thoughtful reader; scatter some seed-thoughts, in 
the hope that, falling haply on good soil, they may spring 
up and bear more fruit than I have been able to produce. 

1. In the gradual individuation of the universal Di- 
vine energy described in Chapter IV, there must of course 
be a corresponding growth of a kind of independent self- 
activity which reaches completeness in man, and in fact, 
constitutes what we call self-consciousness and free will. 
The exact nature of the relation of Deity or of the gen- 
eral forces of Nature to this gradually individuated por- 
tion, I do not undertake to define. And how this idea of 
partial self-activity comports with the absoluteness of 
Deity we can not clearly understand. But this fact need 
not specially disturb us here; for this is only one branch 
of the wider question of the moral agency of man in rela- 
tion to the absolute sovereignty of God, or the freedom 
of man in relation to necessary law in Nature. 

2. Personality behind Nature.— We have already shown 
that, if the brain of a living, thinking man were exposed 
to the scrutiny of an outside observer with absolutely per- 
fect senses, all that he would or could possibly see would be 
molecular motions, physical and chemical. But the sub- 
ject himself, the thinking, self-conscious spirit, would ex- | 
perience and observe by introspection only consciousness, 
thought, emotion, etc. On the outside, only physical phe- 
nomena; on the inside only psychical phenomena. Now, 


OBJECTION ANSWERED. 339 


must not the same be necessarily true of Nature also? 
Viewed from the outside by the scientific observer, noth- 
ing is seen, nothing can be seen, there is nothing else to 
be seen, but motions, material phenomena; but behind 
these, on the other side, on the ¢nside, must not there 
be in this case also psychical phenomena, conscious- 
ness, thought, will; in a word, personality?* In the 
only place where we do get behind physical phenomena, 
viz., in the brain, we find psychical phenomena. Are 
we not justified, then, in concluding that in all cases 
the psychical lies behind the physical? The human 
brain is a wonderful instrument, by means of which, in 
some inscrutable way, viz., in our own experience, we do 
get behind, on the other side, on the inside of some mate- 
rial phenomena, and in so far become partakers of the 
Divine nature. But behind other phenomena of Nature 
we may never hope to penetrate either by observation or 
experience, but only in dim way by highest reason. Sci- 
ence, even in the case of the brain, can not pass from the 
one kind of phenomena to the other. If she would study 
the inside she must abandon the owtside—she must aban- 
don the microscope and take to introspection. If she 
would study the phenomena of the higher platform, she 
must leave the lower and climb up and stand on the 
higher. If this be true of the brain where the two kinds 
of phenomena are brought so close together, how much 
more is it true of the phenomena of the cosmos. We 





* Johnstone Stoney, “ Nature,” vol. xxxi, p. 422. 


‘' 840 EVOLUTION AND RELIGIOUS THOUGHT. 


can never hope, either by observation or by experience, to 
pass beyond the veil. We must abandon the methods of 
science and reach it, if at all, in some other way. Not the 
clear-sighted: but the pure-hearted shall see God in Nature. 

Thus, then, we see that our own self-conscious person- 
ality behind brain phenomena compels us to accept con- 
sciousness, will, thought, personality behind Nature. Now 
I assert that, once get this abstract idea in the mind, 
and by a necessary law of thought it gradually expands 
without limit, and eventually reaches the form of infinite 
consciousness, will, thought, etc., and therefore of an in- 
finite person. This law of indefinite expansion may be 
illustrated by the ideas of space and time. ‘The animal, 
and, indeed, the infant, understands space and time only 
in their relation to itself, but has not yet abstracted these 
from their contents. This comes only with the birth of 
self-conscious personality. But, so soon as the abstract 
idea of space is acquired, by a necessary law of mental 
activity it expands without limit, and finally becomes 
the idea of infinite space. Similarly, so soon as the idea 
of time as abstracted from its contents is conceived, it 
inevitably expands without limit and grows into the 
idea of infinite time. So is it precisely with the idea of 
self-conscious personality. The animal or the very young 
child is indeed conscious of its body and of external 
objects in their mutual relations, but not of self, as ab- 
stracted from its contents. The animal never attains it, 
the child does. Now, so soon as this idea of self-con- 
scious personality—of a spiritual entity underlying mate- 


OBJECTION ANSWERED. 3841 


rial phenomena—appears, by a necessary law of mental 
activity it expands without limit, and inevitably reaches 
the idea of an infinite self, an infinite person, God, be- 
hind the phenomena of Nature. 

But some will object that this idea of infinite person. 
ality is inconceivable. ‘True enough; but the opposite is 
far more inconceivable. The ideas of infinite space and 
infinite time are also inconceivable, yet we must accept 
them, because the idea of all space or all time being lim. 
ited is still more inconceivable; for if we think of space 
or time as limited, immediately there comes the ques. 
tion, “What is there beyond the limit?” There is 
therefore this wide difference between these two in- 
conceivables: the one is so only in the sense of tran- 
scending the power of our mind, but the other is un- 
thinkable, self-contradictory, absurd. So also is it with 
self-conscious. personality. The idea of an infinite self, 
i. e., God, is indeed inconceivable, but only in the sense of 
transcending our power of comprehension; but the idea 
of the consciousness behind the cosmos as being limited or 
finite is more than inconceivable, it is unthinkable, self- 
contradictory, absurd; for immediately comes the ques- 
tion, “ What is there beyond which limits it?” To the 
Greek mind Zeus was limited ; therefore of necessity came 
also the idea of Fate, superior to and limiting Zeus himself. 
To them, therefore, Fate was the real God—the absolute. 

3. Divine Personality.—1 have used the word person- 
ality as expressing the nature of God. But let me not be 
misunderstood. I well know we can not conceive clearly 


342 EVOLUTION AND RELIGIOUS THOUGHT. 


of an infinite, unconditioned personality. Deeply consid- 
ered, it seems nothing short of a contradiction in terms. 
All I insist on is this: In our view of the nature of God, 
the choice is not between personality and something 
lower than personality, viz.,an wnceonscious force oper- 
ating Nature by necessity, as the materialists and panthe- 
ists would have us believe; but between personality as we 
know it in ourselves and something inconceivably higher 
than personality. Language is so poor that we are 
obliged to represent even ows mental phenomena by phys- 
ical images. How much more, then, the Divine nature 
by its human image!  Self-conscious personality is the 
highest thing we know or can conceive. We offer him 
the very best and truest we have when we call him a 
Person; even though we know that this, our best, falls 
far short of the infinite reality. 

4, Cause in Nature.—We have thus far spoken only or 
principally of self-consciousness, but the same precisely is 
true of another essential attribute of personality, viz., free- 
will. Every one admits causative force or forces operat- 
ing in Nature. Science has shown that all the different 
kinds of force are but different forms of one omnipresent 
energy. Now, looking abroad on Nature from the out- 
side, this omnipresent energy seems to modern science as 
simply resident, inherent in matter itself, and therefore 
as operating unconsciously and by necessity. But the 
question occurs, “ Whence did we get the idea of force, 
energy, causation?” I answer unhesitatingly: We get 
it not from without by observation of Nature, but from 


OBJECTION ANSWERED. 343 


within through consciousness ; not from the outside view, 
but from the inside view of phenomena. We can not 
conceive of phenomena without force, of effects without 
cause, because we are intensely conscious of being our- 
selves through our wills an active cause of external phe- 
nomena. If we were merely passive observers, not ac- 
tive causers of changes in the external world, then these 
external phenomena would seem to us merely to shift 
and change and succeed each in a certain order. We 
might note the order and determine the laws of se- 
quence, and thus form a science; but it would never 
enter into our minds to imagine any causal or dynamical 
nexus between them. In the mind of such passive ob- 
server, but not doer—thinker, but not worker—would 
be completely realized the only thorough-going and con- 
sistent materialistic philosophy, i. e., a philosophy in 
which, like Comte’s, cause and force have no place—are 
in fact banished as a superstition from science. But 
the clear consciousness of essential energy, of causative 
force within, the certainty that we ourselves, throngh 
our wills and by the conscious exertion of force do de- © 
termine changes in the external world, compels us to 
attribute all changes to causative force of some kind, 
and naturally enough, until the interference of science, 
to a personal will like our own. Thus by a necessary 
law we project our internal states into external Nature. 

But see now the steps of evolution of this idea. At 
first, i. e., in the uncultured races, and also in childhood, 
external forces take the form of a personal will like our 


344. EVOLUTION AND RELIGIOUS THOUGHT. 


own residing in each object, and controlling its phenom- 
ena as our wills control our bodily movements (fetich- 
ism). ‘Then, as culture advances, it takes next the form 
of several personal wills controlling each the phenom- 
ena of a different department of Nature (polytheism). 
Finally, in the highest stage of culture, it takes the 
form of one personal will controlling the phenomena of 
the whole cosmos (monotheism). ‘To the religious but 
unscientific mind in all these stages the personal will is 
anthropomorphic. But we have already seen (Chapter 
III) how anthropomorphism has been driven by science 
from one department after another, until now at last 
by evolution it is driven out of Nature entirely, and 
to those following this line of thought alone, the phe- 
nomena of Nature are relegated to forces inherent in 
matter, and operating by laws necessary and fatal; and 
not only so, but material forces are made to invade 
even the realm of consciousness, and reduce this also to 
material laws. ‘Thus the savage ejects his own conscious 
personal will into every separate object of Nature; the 
~ modern materialist injects material forces into the realm 
of consciousness. But, as already seen, a rational phi- 
losophy admits these two antithetic views, and strives to 
combine and reconcile them. This reconciliation, as far 
as it is possible for us, is found in a personal will im- 
manent in Nature, and determining directly all its 
phenomena. 

Thus it is evident that the idea of a causal nexus 
between successive phenomena is a primary conception, 


OBJECTION ANSWERED. 845 


and therefore ineradicable and certain. Even from the 
purest evolution point of view it must be true, for, if 
man’s mind grew out of the forces of Nature, this idea 
must represent a fact in Nature. Also, analysis shows 
that all causative force originates in will. Lastly, cul- 
ture and reason, by a necessary law of expansion, car- 
ry us upward to the conception of one infinite sus- 
taining and creative will. Science may sometimes ob- 
scure but can not destroy this idea. Evolution, which 
was supposed by some to have destroyed it for ever, has 
only temporarily obscured it in the minds of the unre- 
flecting, by the supposed identity of evolution with 
materialism. From this temporary eclipse it now 
emerges with still greater clearness and far greater no- 
bleness. For, observe: All the effects known to us in 
Nature are finite ; therefore a personal will, which deter- 
mines these separately by successive acts, as we do, must 
also be finite like ourselves. But a will, which by one 
eternal act ever-doing, never done, determines the evolu- 
tion and the sustentation of an infinite cosmos, must it- 
self be infinite. ‘Thus only in the doctrine of universal 
evolution do we rise to a just conception of God as an in- 
finite cause. 

5. Design in Nature.—As the idea of cause and force 
is related to will, so precisely is the idea of design related 
to thought. We get this also, not from without, but from 
within. Adaptation of means to ends is in our experi- 
ence the result of thought, and we can not conceive it to 
result otherwise. ‘The effect of science can not be to de- 


3846 EVOLUTION AND RELIGIOUS THOUGHT. 


stroy this primary conception—which, indeed, like all pri- 
mary conceptions, is ineradicable, and already more certain 
than anything can be made by proof—but only to exalt and 
purify our conceptions of the designer. For, observe: In 
any case of adaptive structure, whether in the animal body 
or in planetary relations, the evidence of design is not in 
the materials, but in the wse of the materials ; not in the 
parts, but in the adjustment of the parts fur a purpose. 
Design, purpose, adjustment, adaptation, are not ma- 
terial things, but relations or intellectual things, and 
therefore perceivable only by thought, and conceivable 
only as the result of thought. It is simply impossible 
to talk about such adaptive structures without using lan- 
guage which implies design. The very word ‘‘ adaptive” 
implies it. It is impossible even to think of such struct- 
ures without implicitly assuming intelligence as the 
cause. It makes no particle of difference how the mate- 
rial originated, or whether it ever originated at all; it 
matters not whether the adaptation was done at once out 
of hand, or whether by slow process of modification ; it 
matters not whether the adaptive modification was 
brought about by a process of natural selection, or by 
pressure of a physical environment ; whether without law 
or according tolaw. The removal of the result from man- 
like directness of separate action can not destroy the idea 
of design, but only modify our conception of the Designer. 
What science, and especially evolution, destroys, there- 
fore, is not the idea of design, but only our low anthropo- 
morphic notions of the mode of working of the Designer. 


\ 


OBJECTION ANSWERED. 847 


Precisely the same change takes place here under the 
influence of science as has taken place in all our notions 
concerning God. The uncultured savage sees a separate 
god in every object. As culture advances, his gods be- 
come fewer and nobler, until, in the most advanced 
states, man recognizes but one infinite God, the creator 
and sustainer of all. God is still in every phenomenon, 
but no longer as a separate’ God, but only as the sepa- 
rate manifestation of the One. Thus culture takes away 
our gods, but only to compel us to seek him in nobler 
forms until we reach the only true God. But, even after 
the conception of the one God is reached, how many 
seem to regard him as altogether such a one as our- 
selves ; but science shows us that his ways are not like 
our ways, nor his ends as our ends. ‘Thus science, 
more than all other kinds of culture, simplifies while it 
infinitely ennobles and purifies our conceptions of Deity. 

Again, the same change takes place in our sense of 
mystery. I suppose most people imagine that it is the 
special mission of science to destroy all mystery. Many 
seem to think that superstition, or even religion, is in- 
separably connected with ignorance and mystery, and all 
must disappear together before the light of science. 
But not so. There is only a gradual progressive change 
—an evolution in the form of mystery as well as in the 
form of religion. To the savage everything is a sepa- 
rate mystery. The function of science is, indeed, to 
destroy these separate mysteries, by explaining them; 


but, in doing so, it only reduces them to fewer and 
24 3 


348 EVOLUTION AND RELIGIOUS THOUGHT. 


grander mysteries, and these again to still fewer and 
grander, until, in an ideally perfect science, all separate 
and partial mysteries are swallowed up in the one all- 
embracing infinite mystery—the mystery of existence. 
There is still mystery in each object, but no longer a 
separate mystery—only a separate manifestation of the 
one overwhelming mystery. 

Or, again, and finally: The same change occurs in 
our ideas of creation. At first every object is a separate 
creation—a manufacture. With advancing science these 
separate, creative acts become fewer and nobler, until 
now, at last, in evolution, all are embraced and swallowed 
up in one eternal act of creation—a never-ceasing pro- 
cession of the divine energy. Every object is still a 
creation, but not a separate creation—only a separate 
manifestation of the one continuous creative act. 

Now, precisely the same change must take place in 
our conception of design in Nature. ‘To the uncultured 
there is a distinct and separate design in every separate 
work of Nature. But, as science advances, all these 
distinct, separate, petty, man-like designs are merged 
into fewer and grander designs, until, finally, in evolu- 
tion at last, we reach the conception of the one infinite, 
all-embracing design, stretching across infinite space, and 
‘continuing unchanged through infinite time, which in- 
cludes and predetermines and absorbs every possible 
separate design. There is still design in everything, but 
no longer a separate design—only a separate manifesta- 
tion of the one infinite design. 


OBJECTION ANSWERED. 349 


Thus, then, our own se!f-consciousness and will and 
thought give rise, necessarily, to the conception of an 
infinite self-consciousness, will, and thought—i. e., God. 
The necessity to believe in self-conscious spirit behind 
bodily phenomena compels us to believe also in an infi- 
nite self-conscious spirit behind cosmic phenomena. 
Looking at the operations of this ever-active spirit, wheth- 
er in the one case or the other, from the outside, it looks 
like unconscious energy inherent in matter itself, and 
therefore like necessity, or fate. But, looked at from the 
inside i2 the one case, the brain, we perceive only self- 
conscious, free activity of spirit. ‘Therefore, we are com- 
pelled to acknowledge in the other case, the cosmos, also, 
the same source of all activity, the same cause of all phe- 
nomena. We are compelled to acknowledge an infinite 
immanent Deity behind phenomena, but manifested to us 
on the outside as an all-pervasive energy. But some por- 
tion of this all-pervasive energy again individuates itself 
more and more, and therefore acquires more and more a 
kind of independent self-activity which reaches its com- 
pleteness in man as self-consciousness and free-will. We 
said, “a kind of independent self-activity.” How this 
comports with the absoluteness of God we can not under- 
stand, any more than we can understand how it comports 
with invariable law in Nature. We simply accept them 
both as primary truths, even though we can never hope to 
reconcile them completely, because we can not understand 
the exact nature of the relation of spirit to matter. We 
can not look at the outside and the inside at the same 


3850 EVOLUTION AND RELIGIOUS THOUGHT. 


time. If we could understand the relation of psychical 
phenomena to brain-changes, then might we hope to 
understand far more perfectly than now the relation of 
God to Nature. But asin the one case, the brain, al- 
though we can not understand the natwre of the relation, 
yet we are sure of the intimacy of the connection of the 
two series, psychical and physical, term for term; so in 
the other case, the cosmos, although we can not under- 
stand the exact nature, we are sure of the intimacy of the 
connection, term for term—every material phenomenon 
and event with a corresponding psychical phenomenon as 
its cause. 


CHAPTER VIL. 


SOME LOGICAL CONSEQUENCES OF THE DOCTRINE OF 
THE DIVINE IMMANENCY. 


THE doctrine of the Divine immanency carries with 
it the solution of many vexed questions. In fact, in its 
light these questions simply pass out of view as no longer 
having any significance. Several of these questions have 
been alluded to in an indirect way in the previous chap- 
ter and in Chapter III. We take them up distinctly here, 
and show their relation to evolution. 

Religious thought, like all else, is subject to a law of 
evolution, and therefore passes through regular stages. 
Of these stages, three are very distinct and even strongly 
contrasted. They correspond in a general way to the 
three stages of Comte, which he has misnamed the ¢heo- 
logical, the metaphysical, and the positive. We will illus- 
trate by many examples. 


I. Conception of God. 


- This, the most fundamental conception of all religion; 
has passed from a gross anthropomorphism to a true 
spiritual theism, and the change is largely due to science 


352 EVOLUTION AND RELIGIOUS THOUGHT. 


and especially to the theory of evolution. There are 
three main stages in the history of this change: (1.) The 
first is a Jow anthropomorphism. God is altogether such 
a one as ourselves, but larger and stronger. His action 
on Nature, like our own, is direct; his will is wholly 
man-like, capricious and without law. (2.) The second is 
still anthropomorphism, but of a nobler sort. God is not 
altogether like ourselves. He is man-like; yes, but also 
king-like. He is not present in Nature, but sits enthroned 
above Nature in solitary majesty. He acts on Nature, not 
directly but indirectly, through physical forces and natu- 
ral laws. He is an absentee landlord governing his es- 
tate by means of appointed agents, which are the natural 
forces and laws established in the beginning. He inter- 
feres personally and by direct action only occasionally, to 
initiate something new or to rectify something going 
wrong. This idea culminated and found the clearest ex-_ 
pression in the eighteenth century, and was the necessary 
result of the scientific ideas then prevalent, viz., ideas of 
pre-established stability of cosmic order and fixedness of 
organic types. God was the great artificer, the great 
architect, working, as it were, on foreign material and 
conditioned by its nature. He established all things as 
they are in the beginning, and they have continued so 
ever since. 

This conception still lingers in the religious mind, and 
is in fact the prevailing one now. It isa great advance on 
the preceding, but, alas! it removes God beyond the reach 
of our love. He is the architect of worlds, the artificer 


SOME LOGICAL CONSEQUENCES. 353 


of the eye, the sovereign ruler of the universe, but not 
our Father. Weare his creatures, his subjects, but not his 
children. 

(3.) The third and last stage in this development is 
true spiritual theism. God is immanent, resident in Na- 
ture. Nature is the house of many mansions in which 
he ever dwells. The forces of Nature are different forms 
of his energy acting directly at all times and in all places. 
The laws of Nature are the modes of operation of the 
omnipresent Divine energy, invariable because he is per- 
fect. ‘The objects of Nature are objectified, externalized 
—materialized states of Divine consciousness, or Divine 
thoughts objectified by the Divine will. In this view we 
return again to direct action, but in a nobler, a spiritual, 
Godlike form. He is again brought very near to every 
one of us and restored to our love, for in him we live 
and moye and have our being. In him all things consist, 
by him all things exist. This view has been held by noble 
men in all times, especially by the early Greek fathers, 
but is now verified and well-nigh demonstrated by the 
theory of evolution. No other view is any longer tenable. 

The idea of God is of course the most fundamental of 
all religions ideas, and a change in this carries with it 
many other changes. Some of these necessary outcomes, 
especially the nature, the origin, and the destiny of the 
human spirit, and its relation to the Divine spirit, 1 have 
already treated in previous chapters. But there are others 
which flow so directly and obviously that they may be 
presented in brief space. 


354. EVOLUTION AND RELIGIOUS THOUGHT. 


II. Question of First and Second Causes. 


Among the most obvious of these is the question of 
first and second causes. This distinction, I suppose, did 
not exist in early thought. As a popular view, it was 
mainly due to the physical science of the eighteenth cent- 
ury. It was a necessary corollary of the idea of God as 
the great architect sitting outside of Nature and acting on 
Nature as on foreign material. According to this view, 
God is the original and primary cause of all things; but he 
delegates his power to secondary forces, such as gravity, 
heat, electricity, etc., which are therefore the immediate 
causes of phenomena. I believe that most persons hold 
this view still. But it is now being displaced by the idea 
of God immanent or resident in Nature as already ex- 
plained. This view is a complete identification of first 
and second causes. All causes are mere modes of the 
first cause. They seem to us secondary, necessary, and 
unconscious only because they act according to invariable 
law. But law itself is only the mode of operation of a 
perfect will. Thus we have the same three stages of evo- 
lution here also; (1.) First, all is first cause, direct, man- 
like, capricious, lawless. (2.) Then the first cause acts 
king-like, indirectly by many appointed agents subject 
to pre-enacted laws. These agents or secondary causes 
directly determine all natural phenomena. (3.) Lastly, 
come the complete combination and reconciliation of 
these two, All is by first cause and direct action, like the 
first. All is by invariable law like the second, the law 
being only the mode of operation of a perfect will. 


SOME LOGICAL CONSEQUENCES, 855 


_ III. Question of General and Special Providence. 
So also providence, general and special, is only an- 
other phase of the same question and solved in the same 
way. At first all is special providence—the result of ca- 
price or favoritism and without law. Then all or nearly 
all is general providence operating by invariable law; but 
from time to time the general law is broken through for 
special purposes when necessary. Is not this the prevail- 
ing view now? Lastly, these two must be combined and 
reconciled in a third. All is alike general and special: 
general—i. e., according to law; special—i. e., by direct 
action. There is no real distinction between the two. 
The distinction vanishes in the light of a higher view. 


IV. The Natural and the Supernatural. 


In precisely the same category falls the question of the 
natural and the supernatural. The same three stages are 
evident here also, and the same solution: 1. First all is 
supernatural and lawless, and Nature is viewed with 
stupid wonder and abject fear. 2. Then Nature is re- 
duced to mechanical laws and made subject to man. 
Wonder and fear give place to indifference and even per- 
haps to contempt. We practically live without God in 
the world. It requires, now, m7racles or a violent break- 
ing through of law in order to startle us out of our stu- 
pidity and awaken in us a sense of the Divine presence. 
3. But we must come lastly to a higher philosophy. We 
must recognize that all is natural and all is supernatural 
according as we view it, but none more than another. 


356 EVOLUTION AND RELIGIOUS THOUGHT. 


All is natural—i. e., according to law; but all is super- 
natural 





i. e., above Nature, as we usually regard Nature, 
for all is permeated with the immediate Divine presence. 
Wonder in the contemplation of Nature returns, or rather 
exalted reverence and rational worship are given in place 
of open-mouthed wonder and superstitious fear. Once 
clearly conceive the idea of God permeating Nature and 
determining directly all its phenomena according to law, 
and the distinction between the natural and the super- 
natural disappears from view, and with it disappears also 
the necessity of miracles as we usially understand mira- 
cles. In fact, the word as we usually understand it has 
no longer any meaning. 

I must stop a moment to explain, lest I be misunder- 
stood; and to enforce, lest it be thought I speak lightly. 

Miracle, in the sense of violation of law, is simply im- 
possible, because law is the expression of the essential _ 
nature and perfection of God. It is as impossible for 
God to perform a miracle in this sense as it is for him to 
lie, and for the same reason, viz., that it is contrary to 
his essential nature. In what sense, then, is a miracle 
possible? I answer, only as an occurrence or a phe- 
nomenon according to a law higher than any we yet know. 
If we define Nature as phenomena governed by physical 
and chemical laws and forces, then life becomes super- 
natural and miraculous—because higher than Nature as 
we define it. If we reduce the phenomena of life to law 
and include these also in our definition of Nature but 
limit it there, then the free, self-determined phenomena 


SOME LOGICAL CONSEQUENCES. 857 


of reason become supernatural because above our defini- 
tion of Nature. There may well be still other and higher 
modes of Divine activity, the law of which we do not and 
may never understand. These are above our present defi- 
nition of Nature, and therefore to us supernatural or 
miraculous. But, even if miracles in the ordinary sense 
were possible, is it not evident that the ordinary processes 
of Nature are far more wonderful, more truly Godlike, 
than any such miracle? 


V. Question of Design in Nature. 


So, again, the question of design or purpose or mind 
in Nature is similarly solved. It has been said, it is con- 
tinually now being said, that evolution has destroyed for- 
ever the teleological view of Nature—i. e., the idea of 
design in Nature. Yes, if we mean the man-like, cabinet- 
making, watch-making design of Paley and older writers 
—a separate petty design for each separate object. It has 
indeed destroyed this, but only to replace it by a far 
nobler conception—a truly Godlike design, a design em- 
bracing all space and running through all time, including 
and absorbing all possible separate designs and prede- 
termining them by a universal law of evolution. 

Or the same question may be put in another way as 
“Mind vs. Mechanics in Nature.” In the evolution of 
thought on this subject at first all was mind, but lawless, 
capricious, like our own. Then one department after 
another of Nature was reduced to mechanical, physical, 
necessary law, until all have been or will be or conceiv- 


358 EVOLUTION AND RELIGIOUS THOUGHT. 


ably may be thus reduced, and mind seems driven out of 
Nature entirely. The friends of religion in despair cry 
out for at least some small corner left for mind. Thus I 
find in recent numbers of an English scientific periodical, 
“ Nature,” a discussion concerning mind as one of the 
factors of evolution.* Is it not amusing, if it were not so 
sad ?—God the Divine mind as one of the factors of evo- 
lution! The true solution is very simple. All is mind or 
none; so also all is mechanics or none. It is all mind 
through mechanics. It is all mechanics from the out- 
side; it is all mind from the inside. To science all is 
mechanics; to theology all is mind, It is the duty of 
philosophy to reconcile these two opposites by the higher 
view that mechanics is but the mode of operation of the 
Divine mind. There is only one form of evolution, viz., 
human progress, in which mind—but the human, not the 
Divine mind—is one of the factors of evolution. But to 
think and speak thus of God in relation to Nature is to 
place him on the human plane. It is gross anthropomor- 
phism. t 


VI. Question of the Mode of Creation. 


I might multiply examples almost without limit, of 
questions the solution of which depends on this one of the 
relation of God to Nature. I give one more—Creation. 


* “Nature,” vol. xxxiv, p. 385. 1886. 

+ So, again, see a book recently published (‘‘ Nature,” vol. xliii, p. 
460, 1891), entitled ‘““Whence comes Man, from Nature or from God?” 
The answer is plain. From both—from God through Nature. Evolu- 
tion is the method of creation. Lee Ao sas er 


SOME LOGICAL CONSEQUENCES, 359 


The creation of the universe at once—in the begin- 
ning—out of nothing—and then rest ever since. This 
old anthropomorphic idea is now replaced by that of con- 
tinuous creation —unhasting, unresting, by an eternal 
process of evolution. For if the universal law of gravi- 
tation is the Divine mode of sustentation of the universe, 
the no less universal law of evolution is the Divine pro- 
cess of creation. 


CHAPTER VIII. 


THE RELATION OF EVOLUTION TO THE IDEA OF THE 
CHRIST. 


Wuat think ye of Christ? This is indeed in 
many ways a test-question, and we ought frankly to 
meet it. I have feared heretofore to touch this ques- 
tion. I now only throw out some brief suggestions— 
scatter some seed-thoughts. Does Evolution have any- 
thing to say on this also? I think it does. This I pro- 
ceed to show: . 

As organic evolution reached its goal and comple- 
tion in man, so human evolution must reach its goal and 
completion in the zdeal man—i. e., the Christ. Accord- 
ing to this view, the Christ is the ideal man, and therefore 
—(mark the necessary implication)—and therefore the 
Divine man. We are all as men (as contradistinguished 
from brutes)—we are ail, I say, sons of God ; the Christ 
is the well-beloved Son. We are all in the image of God; 
he is the express and perfect image. We are all par- 
takers in various degrees of the Divine nature; in him 
the Divine nature is completely realized. It is not neces- 
sary that the ideal man—the Christ—should be perfect 


EVOLUTION OF THE IDEA OF THE CHRIST. 361 


in knowledge or in power; on the contrary, he must 
grow in wisdom and in stature, like other men; but he 
must be perfect in character. Character is essential 
spirit. All else, even knowledge, is only environment for 
its culture. In the dazzling light of modern science we 
are apt to forget this. Character is the attitude of the 
human spirit toward the Divine Spirit. If.I should add 
anything to this definition, 1 would say it is spiritual 
attitude and spiritual energy. In the Christ this attitude 
must be wholly right; the harmony—the union with the 
Divine—must be perfect. This perfect union gives, of 
necessity, also fullness of spiritual energy. 

Now, I wish to show that, although the Christ as thus 
defined must be human—yes, even more intensely hu- 
man than any one of us—yet by the law of evolution we 
ought to expect him to differ from us in an inconceivable 
degree, and especially in a superhuman way. This I do 
by a series of illustrations. 

We have said that the Christ is the ideal and therefore 
the Divine man—that he is the goal and completion of 
humanity. But in evolution a goal is not only a com- 
pletion of one stage, but also the beginning of another 
and higher stage—on a higher plane of life with new and 
higher capacities and powers wnimaginable from any 
lower plane. Let me illustrate : 

1. As man is the ideal—the goal and completion of 
animal evolution, and yet is he also a birth into a higher 
plane of life—the spiritual ; so the Christ, the ideal man, 
may be only the goal and completion of human evolution, 


362 EVOLUTION AND RELIGIOUS THOUGHT. 


and yet is he also a birth into a new and higher plane— 
the Divine. 

2. As the human spirit pre-existed in embryo in ani- 
mals, slowly developing through all geological times, 
until it came to birth and immortality in man, so the 
Divine spirit is in embryo in man in various degrees of 
development, and comes to birth and completion of 
Divine life in the Christ. 

3. As animals reached, finally, conscious relations with 
God in man, even so man reaches union with God in the 
Christ. As man, the ideal animal, is a union of the 
animal with the spiritual; so the Christ, the ideal of 
human evolution, is a union of the Auman and the 
Divine. 

4, Finally: As with the appearance of man there 
were introduced new powers and properties unimagina- 
ble from the animal point of view, and therefore from 
that point of view seemingly supernatural—i. e., above 
their nature—so with the appearance of the Christ we 
ought to expect new powers and properties unimaginable 
from the human point of view, and therefore to us seem- 
ingly supernatural—i. e., above our nature. 

The Christ as defined above—i. e., as the ideal man— 
is undoubtedly a true object of rational worship. There 
are two and only two fundamental moral principles, viz., 
love to God and love to man. Both of these must be em- 
bodied in a rational worship. The one must be embodied 
in the worship of an Infinite Spirit—God; the other in 
the worship of the ideal man—the Christ. 


EVOLUTION OF THE IDEA OF THE CHRIST. 368 


But some one will object that, admitting all this, it is 
impossible that the goal, the ideal, should appear until the 
end of the course of evolution. ‘To him I answer: This 
is indeed true of animal evolution, but not of human eyo- 
lution. We have already seen (see p. 88 ef seq.) that there 
is an essential difference in this regard between these two 
kinds of evolution. In addition to all the factors of or- 
ganic evolution, in human progress there is a new and 
higher factor added, which immediately takes precedence 
of all others. This factor is ¢he conscious voluntary co- 
operation of the human spirit in the work of its own evo- 
lution. 'The method of this new factor consists essen- 
tially in the formation, and especially in the voluntary 
pursuit, of ideals. In organic evolution species are trans- 
formed by the environment. In human evolution char- 
acter is transformed by its own ideal. Organic evolution 
is by necessary law—human evolution is by voluntary 
effort, 1.e., by free law. Organic evolution is pushed on- 
ward and upward from behind and below. Human evo- 
lution is drawn upward and forward from above and in 
front by the attractive force of ideals. Thus the ideal of 
organic evolution can not appear until the end; while the 
attractive ideals of human evolution mest come—whether 
only in the imagination or realized in the flesh—but must 
come somehow in the course. The most powerfully at- 
tractive ideal ever presented to the human mind, and, 
therefore, the most potent agent in the evolution of human 
character, is the Christ. This ideal must come—whether 


in the imagination or in the flesh I say not, but—must 
25 


364 EVOLUTION AND RELIGIOUS THOUGHT. 


come somehow in the course and not at the end. At the 
end the whole human race, drawn upward by this ideal, 
must reach the fullness of the stature of the Christ. 

But it will be again objected that all ideals are relative 
and temporary ; that we are in fact drawn onward and up- 
ward by many successive ideals, one beyond another, in 
the course. Ideals are but mile-stones which we put suc- 
cessively behind us while we press on to another; they 
are successive rounds of an infinite ladder which we put 
successively beneath us while we rise higher. This one 
also we shall eventually put behind us and pass on. 

To this I have two answers: Admitted that in many 
ways such is the course of progress; but who has been 
able to reach this ideal and conceive a higher? When this 
one is reached and completely realized in our personal 
character, it will be time enough to propose another. 

Again, it is true that in many ways we have advanced 
and are still advancing by the use of partial ideals; but 
this use of partial and relative ideals is itself in only a 
temporary stage of evolution. Ata certain stage we catch 
glimpses of the absolute moral ideal. Then our gaze be- 
comes fixed, and we are thenceforward drawn upward for- 
ever. The human race has already reached a point when 
the absolute ideal of character is attractive. This Divine 
ideal can never again be lost to humanity. 


CHAPTER IX. 
THE RELATION OF EVOLUTION TO THE PROBLEM OF EVIL. 


THE problem of evil has tasked the power and baffled 
the skill of the greatest thinkers in every age. It would 
be folly in me to imagine that I can solve it. Its com- 
plete solution is probably impossible in the present state 
of science. Yet I can not doubt that on this, as on every 
important question relating to man, the theory of evolu- 
tion will throw new and important light. All I can hope 
to do is to throw out some brief suggestions on the sub- 
ject. 

If evolution be true, and especially if man be indeed 
a product of evolution, then what we eall evil is not a 
unique phenomenon confined to man, and the result of 
an accident, but must be a great fact pervading all na- 
ture, and a part of its very constitution. It must have 
existed in all time in different forms, and subject like 
all else to the law of evolution. _ Let us, then, trace rap- 
idly some of the steps of this evolution. 

1. Haternal Physical Evil in the Animal Kingdom. 
—As already seen in previous chapters, the necessary 
condition of evolution of the organic kingdom is a strug- 


866 EVOLUTION AND RELIGIOUS THOUGHT. 


gle for life—a conflict on every side, with a seemingly 
inimical environment and a survival of only the strong- 
est, the swiftest, or the most cunning—in a word, the 
fittest. Now, suppose the course of organic evolution 
finished in the introduction of man, and from this vant- 
age-cround we look back over the course and consider 
its result. Shall we call that evil which was the neces- 
sary condition of the progressive elevation which cul- 
minated so gloriously ? Evil doubtless it seemed to the 
individual, struggling animal, but is this worthy to be 
weighed in comparison with the evolution of the whole 
organic kingdom until it culminated in man? Is it not 
rather a good in disguise ? I suppose human arrogance 
may be willing enough to admit it in ¢his case, where 
animals only are sufferers. 

2. Physical Evil in Relation to Man.—But organic 
evolution, completed in man, was immediately trans- 
ferred to a higher plane, and continued as social evolu- 
tion ; material evolution is transformed into psychical 
evolution ; unconscious evolution, according to meces- 
sary law, to conscious voluntary progress toward a rec- 
ognized goal, and according to a freer law. But in this 
transformation the fundamental conditions of evolution 
do not change. Man also is surrounded on every side 
with what at first seems to him an evil environment, 
against which he must ever struggle or perish. Heat 
and cold, tempest and flood, volcanoes and earthquakes, 
savage beasts and still more savage men. What is the 
remedy—the only conceivable remedy ? Knowledge of 


EVOLUTION AND THE PROBLEM OF EVIL. 367 


the laws of Nature, and thereby acquisition of power 
over Nature. But increasing knowledge and power are 
equivalent to progressive elevation in the scale of psychi- 
cal being. This conflict with what seems an evil en- 
vironment is, therefore, the necessary condition of such 
elevation. It is not too much to say that, without this 
condition, except for this necessity for struggle, man 
could never have emerged out of animality into human- 
ity, or, having thus emerged, would never have risen 
above the lowest possible stage. Now suppose, again, 
this ideal to have been attained—suppose knowledge of 
physical laws and power over physical forces to be com- 
plete—suppose physical nature completely subdued, put 
beneath our feet, and subject to our will, and, from the 
high intellectual position thus attained, we look back 
over the whole ground and consider the result. Shall 
that be called evil which was obviously the necessary 
condition for attaining our then elevated position ? 
Evil it doubtless seemed to the individuals who fell, 
and still seems to us who now suffer, by the way in 
the conflict ; but is physical discomfort or even physical 
death of the individual to be weighed in comparison 
with the psychical elevation of the individual, and espe- 
cially of the race? Evidently, then, physical evil even 
in the case of man is only seeming evil, but real good. 

3. Organic Evil— Disease. —But there is a more 
dreadful form of evil than that which results from ea- 
ternal physical nature—an evil far more subtle and diffi- 
cult to understand, and therefore to conquer. IJ mean 


368 EVOLUTION AND RELIGIOUS THOUGHT. 


internal organic eyil—disease in its diversified forms and 
with its attendant weakness and suffering, inscrutable 
often in its causes, insidious in its approaches, conta- 
gious, infectious, spreading from house to house, carry- 
ing suffering and death in its course, and leaving sorrow 
and desolation behind. Is there any remedy which can 
transmute this evil into good? ‘There is. It is again 
knowledge—knowledge of the laws, and power over the 
forces, of organic nature. Is it not evident that complete 
knowledge of the laws of health and the causes of dis- 
ease would put this evil also under our feet? Is it not 
evident that a perfect knowledge of the laws of health, 
and a perfect living according to these laws, would so 
entirely subdue this evil that men would no longer die 
except by natural decay or by accident? Is it not evi- 
dent, also, that the race will not attain this knowledge ~ 
unless it be forced upon us by the necessity of avoiding 
the dread evil of disease ? | 

Now suppose, again, this ideal attained, suppose this 
dread evil subdued by complete knowledge, and again 
from our elevated intellectual position we look back over 
the ground. Shall we call that evil which was the ne- 
cessary condition of our intellectual elevation? vil, 
doubtless, it seems to us individuals who have suffered 
and are still suffering through our ignorance; but is 
such individual suffering or even individual death to 
be weighed against the psychical elevation of the in- 
dividual and evolution of the race? Ought not the 
individual to be willing to suffer thus much vicarious- 


EVOLUTION AND THE PROBLEM OF EVIL. 369 


ly for the race? Is not this seeming evil also a real 
good ? 

May we not, then, confidently generalize? May we 
not say that all physical evil is good in its general effect 
—that every law of Nature is beneficent in its general 
operation, and, if sometimes evil in its specific operation, 
is so only through our ignorance? Partly by survival of 
the fittest, and partly by intelligence, man, like other 
animals, brings himself in accord with the laws of Na- 
ture, and thus appropriates the good and avoids the evil, 
and Nature becomes beneficent only. But, also unlike 
any other animal, man by rational knowledge makes the 
laws of Nature his servants, and uses them for his own 
purposes, thus increasing his power and elevating the 
plane of his life. 

4, Moral Evil.—But there is still another form of 
evil, the most dreadful of all. This one may be called 
the evil, in some sense, the only evil. It is that of which 
all other forms are but the shadows cast backward and 
downward along the course of evolution and on lower 
stages of existence. This consummation of all evil is 
sin — moral disease—more dreadfully contagious and 
deadly than any organic disease. What shall we say 
now? Is there any rational explanation of this evil? 
Is there any possible reason or excuse for an all-wise, all- 
powerful Ruler afflicting man alone of all His creatures 
with this greatest of all evils? In all other cases, the 
individual and the race sacrifice themselves for a time 
physically for the sake of final spiritual elevation ; but 


3870 EVOLUTION AND RELIGIOUS THOUGHT. 


this 1s spiritual debasement. In all other cases, there is a 
sacrifice in the cowrse in order to attain the goal, but this 
is a missing of the goal itself. Is there any view which 
mitigates this evil, any philosophic alchemy which can 
transmute this evil into good ? Age after age the human 
mind has prostrated itself in helpless paralysis before 
this problem. Most thinkers have been content to say, 
‘Thou hast ordered it so. Thou art good. It must be 
right.” But many, and among them some of the best 
minds, have said, ‘‘ Hither God is not all-good, or else 
not all-wise, or else not all-powerful, or else there is no 
God at all.” Does evolution shed any light on this— 
dread problem? I believe it does. 

We have said that all other evils are but shadows of 
this one, cast backward and downward on earlier stages 
of evolution and lower forms of existence. But from 
the evolution point of view these earlier and lower forms 
of evil are rather to be regarded as foreshadowings of the 
reality to come. They are but earlier and lower stages 
of the evolution of the same thing—embryonic condi- 
tions of the now full-grown evil. If so, then the same 
law must apply here also, though, as we shall see, with 
a difference. Here, also, the individuai as well as the 
race finds himself surrounded by what seems an evil en- 
vironment, against which he must struggle. The spirit 
of man is inclosed and conditioned by a lower environ- 
ment, which he must subdue or perish. Here, then, is 
again a deadly conflict : ‘‘a law in the members warring 
against the law of the spirit, and bringing it into captiv- 


EVOLUTION AND THE PROBLEM OF EVIL. 371 


ity”; a law of selfism warring against the law of love, and 
bringing it into subjection; solicitations to debasement 
on the one hand, and solicitations to wrong others on the 
other. How shall it be overcome? What is the reme- 
dy? Again I answer, Knowledge of and conformity to 
the laws of the moral world. But, as in other cases, so 
in this: this knowledge of and conformity to law, which 
is the true goal of humanity, will not be attained unless 
it is forced upon us by necessity and in self-defense— 
l.e., by evil. 

Now suppose, once more, this knowledge and con- 
formity be complete, and the ideal of humanity be at- 
tained, and from this final and highest position we look 
back over the whole ground. Shall that be called evil 
which from the very nature of a moral being and the 
laws of evolution was obviously the necessary condition 
of attaining the goal? Shall we not from this final posi- 
tion call it a good in disguise ? Lyvil, doubtless, it seems 
to us who suffer and stumble and mayhap fall by the 
way ; but shall the mishap of the individual be weighed 
as an equivalent against the evolution of the race and the 
attainment of its goal? 

Ah! there is the rub. It is all well enough to talk 
of sacrificing the physical individual to the race, but 
not so the spiritual. If we believe in the immortality of 
the human spirit, if we do indeed stand related to God 
in the manner explained in Chapter IV, then moral 
evil in the individual has an entirely peculiar and an 
eternal significance—then the individual human spirit 


872 EVOLUTION AND RELIGIOUS THOUGHT. 


has an infinite worth and can not be sacrificed to the 
race ; for the evolution of the race itself is only in order 
to the perfecting of individual human souls. What 
shall we say now? I answer: The sacrifice is not ne- 
cessary. There is in the realm of morals alone a way of 
escape—a saving element which redeems the individual 
without violating the law. Let me explain. 

It will, I think, be admitted by all that innocence 
and virtue are two very different things. Innocence is 
a pre-established, virtue a self-established, harmony of 
spiritual activities. ‘The course of human development, 
whether individual or racial, is from imnocence through 
more or less discord and conflict to virtue. And virtue 
completed, regarded as a condition, is holiness, as an 
activity, is spiritual freedom. Not happiness nor inno- 
cence but virtue is the goal of humanity. Happiness 
will surely come in the train of virtue, but if we seek 
primarily happiness we miss both. ‘Two things must be | 
borne steadily in mind: virtue is the goal of humanity ; 
virtue can not be given, it must be self-acquired. 

Now we have already seen that in all evil the remedy, 
which not only cures it but transmutes it into good, is 
knowledge of law and conformity of conduct thereto— 
a true science and a successful art—in a word, knowledge 
of the laws of God and obedience to these laws. In the 
physical world ignorance of these laws is necessarily fatal, 
but not so in the moral world. Ignorance here is not 
necessarily fatal though dangerous. By the very nature 
of a moral being, the essential thing is not knowledge but 


EVOLUTION AND THE PROBLEM OF EVIL. 373 


character or virtue—the will to know and the effort to 
obey. In the physical realm, knowledge is the goal; in 
the moral realm, knowledge is only in order to virtue. 
Therefore, in the case of the individual struggling with 
moral evil within and without, the victory is always in 
his power. If he fails, it is his own fault. His utmost ef- 
fort in this field must be successful, because the result is 
not external, but internal and in the realm of moral 
freedom. ‘The spirit of man is self-acting and in some 
sense, though not absolutely, self-existing, and can not be 
ruined except by its own act. In the moral world, where 
the goal is not knowledge but character, attainment must 
be in proportion to honest endeavor in the right spirit. 

Eyil, then, has its roots in the necessary law of evo- 
lution. It is a necessary condition of all progress, and 
pre-eminently so of moral progress. But some will ask, 
‘* Why could not man have been made a perfectly pure, 
innocent, happy being, unplagued by evil and incapable 
of sin?” I answer: The thing is impossible even to 
omnipotence, because it is a contradiction in terms. 
Such a being would also be incapable of virtue, would 
not be a moral being at all, would not in fact be man. 
We can not even conceive of a moral being without free- 
dom to choose. We can not even conceive of virtue 
without successful conflict with solicitations to de- 
basement. But these solicitations are so strong and so 
often overcome us, that we are prone to regard the solici- 
tations themselves as essential evil instead of our weak 
surrender to them. 


374 EVOLUTION AND RELIGIOUS THOUGHT. 


All evolution, all progress, is from lower to higher 
plaae. From a philosophic peint of view, things are not 
good and evil, but only higher and lower. All things are 
good in their true places, each under each, and all must 
work together for the good of the ideal man. Hach 
lower forms the basis and underlying condition of the 
higher ; each higher must subordinate the lower to its 
own higher uses, or else it fails of its trueend. The 
physical world forms the basis and condition of the or- 
ganic, yet the organism rises te a higher plane only by 
ceaseless conflict with and adaptation to the physical en- 
vironment, which therefore seems in some sense evil. 
The organic world in its turn underlies and conditions 
and nourishes the rational meral world. As the senses 
are the necessary feeders of the intellect, so the appe- 
tites are the necessary feeders of the moral nature. 
Yes, even the lowest sensual appetites are the necessary 
basis and nourishers of our highest moral sentiments. — 
And yet the struggle for mastery of the higher spiritual 
with the lower animal is often so severe that the latter 
seems to many as essential evil to be extirpated, instead 
of a useful servant to be controlled. This view is asceti- 
cism. Now the whole view of evil usually held is a kind 
of asceticism, and therefore, like asceticism, must be only 
a transition phase of human thought. All that we call 
evil both in the material and the spiritual world is good, 
so long as we hold it in subjection as servants to the spirit, 
and only becomes evil when we succumb. All evil con- 
sists in the dominance of the lower over the higher ; all 


EVOLUTION AND THE PROBLEM OF EVIL. 875 


good in the rational use of the lower by the higher. 
Asceticism may, mdeed, be the best philosophy for some. 
If we can not subdue the lower nature, we must try to 
extirpate it, and thus at any cost set free the higher from 
humiliating bondage. If we can not practice the higher 
virtue of temperance in all things, we must even try the 
lower virtue of ¢otal abstinence in some things. If our 
right eye offends, we must not hesitate to pluck it out ; 
but let us not imagine that one eye is better than two 
—let us clearly understand that thereby our spiritual 
nature is sadly maimed, and therefore that the highest 
virtue, which is spiritual beauty and strength, can not 
thus be attained. ‘T'rue virtue consists, not in the ex- 
tirpation of the lower, but in its subjection to the 
higher. ‘The stronger the lower is, the better, 7f only 
it be held in subjection. For the higher is nourished 
and strengthened by its conneetion with the more robust 
lower, and the lower is purified, refined, and glorified 
by its connection with the diviner higher, and by this 
mutual action the whole plane of being is elevated. It 
is only by action and reaction of all parts of our com- 
plex nature that true virtue is attained. 





IND 


Acceleration, law of, 178. 

African fauna explained, 204. 

Agassiz, his greatest result, 29, 43 ; 
relation to evolution, 32, 37, 43; 
relation to Darwin, 46; compared 
with Kepler, 47. 

Ages of geological history, 16. 

Alpine species explained, 215. 

Amphibians, development of, 150. 

Analogy and homology, 99. 

Anima of animals, 313, 317. 

Animal architecture, styles of, 209. 

Animal kingdom, primary divisions 
of, 107. 

Animals, relation of man to, 311; 
spirit embryonic in, 311. 

Antiquity of man, religion and, 282; 
of the earth, religion and, 281. 

Aortic arches, proofs of evolution 
from, 151. 

Arthropods, 132. 

Artificial production of varieties, 
222. 

Australia, fauna and flora of, ex- 
plained, 200; when isolated, 202. 


SS SS ee ee a eet 


Barriers limit faunal and floral re- 
gions, 188, 


eX, 


Beauty, origin of, 269. 

Birds’ tails, changes of, 274. 

Brain, vertebrate, proofs of evolu. 
tion from, 162; vertebrate, 
changes of, in phylogenic series, 
168; relation to mind, 327, 338, 

Brain-physiology as a basis for ma- 
terialism, 306. 

Branching tree illustrates evolution, 
13-15, 18, 110, 250 

Brooks, W. K., on the cause of va- 
riations, 262. 


Californian coast-islands, fauna and 
flora of, 211. 

Causation, idea of, from within, 
342. 

Cause, first and second, 854. 

Cells, somatic and germ, 98. 

Centers of creation, specific, 194. 

Cephalization, 171. 

Chambers, his views on evolution, 
34, 

Changes slow at present, 266. 

Christ, the, 859; relation of evolu- 
tion to, 359; as an agent in hu- 
man progress, 363. 

Close-breeding, effects of, 236, 243, 


378 


Coast-islands of California, fauna 
and flora of, 211. 

Comparison, method of, 41. 

Conflict between religion and sci- 
ence, 280, 

Continental faunas and floras, 188. 

Continental island life, 208. 

Continuity, law of, 53; law of, ap- 
plied to inorganic forms, 54; to 
organic forms, 56. 

Cope’s law of acceleration, 178. 

Creation, special, 30, 69; specific 
centers of, 194; changes in our 
notions of, 3848; question of 
mode, 358. 

Cross-breeding, law of, 236. 

Cross-fertility of artificial varieties, 
232. 

Cross-sterility, 77, 234. 

Cyclical movement, law of, 16, 22. 


Darwin, relation to Agassiz, 46; 
compared with Newton, 48; fac- 
tors of evolution discovered by, 
74; objections to his theory of 
evolution, 76. 

Derivation, origin of inorganic 
forms by, 54; origin of organic 
forms by, 56. 

Design, idea of, from within, 345; 
argument from, not destroyed by 
evolution, 346; changes in our 
ideas of, 348; in Nature, ques- 
tion of, 357. 

Differentiation, law of, 11, 19; law 
of, in embryonic development, 
19; law of, illustrated, 144; of 
the animal kingdom illustrated, 
176, 

Disease, necessity of, 867. 


INDEX. 


Divine energy, forms of, 318. 

Divisions of the animal kingdom, 
4 We 

Dogmatism, theological and scien- 
tific, 293. 

Domestication, changes produced 
by, 222. 


Egg, development of, 3, 19. 
Egyptian species unchanged in 


three thousand years, 265. 

Embryology, proofs of evolution 
from, 148. 

Environment, physical, 73. 

Evil, problem of, relation of evolu- 
tion to, 365; physical, necessity 
of, 366; a condition of progress, 
366, 8733 organic, necessity of, 
367; moral, necessity of, 369. 

Evolution, what is, 8, 8; scope of, 
3; type of, 3, 8; examples of, 5; 
popularly limited to the organic 
kingdom, 7; progressive change 
in, 9; laws of, 11; illustrated by 
branching tree, 13-15, 18, 90, 
250; misconception of, 14; pro- 
duced by resident forces, 27; 
germs of the idea, 32; relation of 
Agassiz to, 32, 37, 43 ; Lamarck’s 
views on, 33; Chambers’s views 
on, 34; obstacle to, removed, 35; 
confliction with religion imagi- 
nary, 45 ; how related to gravita- 
tion, 49; general evidences of, 
53; artificial, 60; observed, 62; 
certainty of, 65; special proofs 
of, 67; factors of, 73, 81; hu- 
man contrasted with organic, 88 ; 
monotypal and polytypal, 85; 
proofs of, from the vertebrate 


INDEX. 879 


skeleton, 111; from the articu- 
late skeleton, 132; from em- 
bryology, 148; from develop- 
ment of amphibians, 150; from 
aortic arches, 151; from verte- 
brate brain, 162; from rudi- 
mentary organs, 179; from geo- 
graphical distribution of organ- 
isms, 183; explains geographical 
diversity, 195; objection to this 
view, 217; answer, 219; proofs 
of, from artificial modifications, 
222; factors of, operative in do- 
mestication, 228; paroxysmal, 
257; material, nearly completed, 
267 ; thoroughly established, 275 ; 
relation to religion, 276, 282 ; re- 
_ lation to materialism, 284; ne- 
cessitates great change in relig- 
ious thought, 295; of forces, 
315; relation to revelation, 331 ; 
pantheistic objection answered, 
835; relation to problem of evil, 
365. 

Experimental method largely fails 
on plane of life, 40. 


Factors of evolution, 73; their 
grades and order of introduction, 
81; Lamarckian, 81; selection, 
82-85; Darwinian, 83; rational, 
86. 

Faculties, evolution of, 23. 

Faunas and floras, geographical, 
183; continental, 188; marine, 
192; special cases of distinct, 
192; of Australia, 200; of Afri- 
ca, 204; of Madagascar, 205; of 
continental islands, 208; of the 
coast-islands of California, 211; 


26 


of oceanic islands, 213; of lofty 
mountains, 215. 

Fish-tails, changes of, in develop- 
ment, 172; in evolution, 174. 

Fishes, age of, 17. 

Floras and faunas, geographical, 
185. 

Force, vital, correlation of, 36; 
planes of, 314; evolution of, 315; 
idea of, from within, 342. 

Forces, resident, evolution by, 27; 
of Nature are forms of Divine 
energy, 317; different planes of, 
314, 

Fore-limbs, vertebrate, homologies 
of; 113: 


Generation, spontaneous, 15. 

Geographical faunas and floras, 
183; diversity, theory of, 193; 
diversity explained by evolution, 
195; present diversity deter- 
mined by Glacial epoch, 198 ; ob- 
jection to this view, 217 ; answer, 
219. 

Geological record, imperfection of, 
252. 

Glacial epoch determined distribu- 
tion of species, 195, 198, 215; 
changes during, in America, 198 ; 
in Europe, 199. 

God, relation of, to Nature, 297; 
immanence of, in Nature, 300; 
relation of, to man, 326; person- 
ality of, 832; necessary belief in, 
344; different forms of concep- 
tion, 351. 

Good and the true, relation of, 277. 

Grasshopper, external anatomy of, 
143. 


580 


Gravitation, relation of, to evolu- 
tion, 49; and religion, 281. 
Gyroscope, 288. 


Heliocentric theory and religion, 
230. 

Hind-limbs, vertebrate, homologies 
of, 121. 

Horse, genesis of, 126. 

Homologies of vertebrate skeleton, 
111; of vertebrate fore-limbs, 
113; of vertebrate hind-limbs, 
121; of articulate skeleton, 132. 

Homology and analogy, 99; only 
within primary divisions, 108, 

Hyatt, A., on Planorbis, 254. 


Ideal, relative and absolute, 364. 

Idealism, true and false, 301. 

Immortality in accord with law, 
316. 

Individuality, organic, 325; spirit- 
ual, 325. 

Innocence and virtue compared, 
372. 

Inorganic forms, law of continuity 
applied to, 54. 

Intermediate forms between arti- 
ficial varieties, 232, 

Islands, continental and oceanic, 
207. 


Kepler compared with Agassiz, 47 
Lamarck, evolutionary views of, 33, 


74, 
Law of differentiation, 11, 19; of 


INDEX. 


plied to inorganic forms, 54; to 
organic forms, 56; of diifcrenti- 
ation illustrated, 144; of acceler- 
ation, 178; of cross-breeding, 218, 
236. 

Laws of evolution, 11, 19. 

Lepidosiren, 101. 

Life, nature of, 85; imperfectly 
subject to experiment, 40; rela. 
tion of, to philosophy, 277. 

Limbs, vertebrate, homology of, 
113. 

Links, connecting, 12, 57, 145; con- 
necting, elimination of, 248 ; con- 
necting, usually absent from geo- 
logical faunas, 251. 

Liquidambar, 218, 220. 

Lobster, external anatomy of, 136. 

Lungs, formation of, 100. 


Madagascan fauna explained, 205. 

Mammals, age of, 17. 

Man, age of, 18; relation of, to Na- 
ture, 304; relation of, to animals, 
311; spirit of, in relation to the 
forces of Nature, 313, 316; rela- 
tion of God to, 331. 

Marsupials, 201. 

Materialism, relation of, to evolu- 
tion, 284; basis for, in brain- 
physiology, 806; basis for, in 
evolution, 311 

Methods, scientific, 38. 

Migration favors diversification, 77. 

Mind, relation of, towbrain, 327, 
338; versus mechanics in Nature, 
340, 


progress of the whole, 13, 22; of ; Miracles, question of, 356. 
cyclical movement, 16, 22; of | Mollusks, age of, 16. 
continuity, 53; of continuity ap- | Monotremes, 201. 


INDEX. 


Mystery, changes in our sense of, 
847, 


Nature, relation of God to, 297; 
immanence of God in, 300; rela- 
tion of man to, 304; has no 
meaning without spirit, 329; 
mind versus mechanics in, 340. 

Natural and supernatural, 355. 

Neo-Darwinism, 93; relation of, to 
human progress, 97. 

Newton compared with Darwin, 48. 

Nominalism and realism reconciled, 
329, 


Obstacle to evolution removed, 35. 

Oceanic island life, 213. 

Ontogenic series, 9, 40. 

Organic forms, views of origin of, 
29, 68, 72, 292; law of continuity 
applied to, 56. 

Organs, incipient, 2'70. 

Origin of varieties unexplained, 
270. 


Pantheism, true and false, 302, 
335. 

Paroxysmal evolution, 257. 

Personality behind Nature, 338. 

Personality of God, 337, 341. 

Philosophy and life, relations of, 
277. 

Phylogenic series, 10, 41. 

Planorbis of Steinheim, 254. 

Primal animals, 145. 

Progress of the whole, law of, 13, 
22. 

Progressive change in evolution, 9. 

Providence, question of general and 
special, 355. 


381 


Ranges of organic forms, 186. 

Realism and nominalism reconciled, 
329. 

Record, geological, imperfection of, 
252, 

Religion, so-called conflict of, with 
evolution, 45, 280. 

Religious thought to be reconstruct- 
ed, 295. 

Reproduction, methods of, 287. 

Reptiles, age of, 17. 

Revelation, relation of evolution to, 
3831; not inconsistent with the 
laws of Nature, 382; nature of, 
333. 

Reversion of artificial forms, 229. 

Romanes, G. J., his idea of physio- 
logical selection, 76, 84; the idea 
applied, 245. 

Rudimentary organs, proofs of evo- 
lution from, 179; organs in man, 
181, 


Selection, sexual, 74, 85; natural, 
74, 79, 83; physiological, 75, 79, 
84; natural, compared with arti- 
ficial, 225; physiological, ap- 
plied, 245. 

Self-consciousness the sign of spirit- 
individuality, 325. 

Sequoia, 219, 220. 

Sexes, characters 
262 

Shrimp, external anatomy of, 134. 

Sin a condition of moral evolution, 
350. 

Skeleton, vertebrate, homologies of, 
111; articulate, homologies of, 
132; articulate, general structure 
of, 134. 


of, compared, 


382 


Society, progress of, 25. 

Space and time the two fundamental 
conditions of material existence, 
48. 

Species, natural, more permanent 
than artificial varieties, 229; more 
distinct, 232; cross-sterile, 232. 

Spirit embryonic in animals, 311; 
of man related to anima of ani- 
mals, 313; to forces of Nature, 
313, 316; origin of illustrated, 
320-322; Plato’s view, 326; or- 
thodox view, 326; no meaning in 
Nature without, 329. 

Steinheim, Planorbis of, 254. 

Supernatural and the natural, 355. 


Taxonomic series, 9, 40. 

Temperature-regions, 184, 

Tread, plantigrade and digitigrade, 
123, 

True and the good, relation of, 
277. 


INDEX. 


Truth tested by effect on life, 277; 
not compromise, 291. 
Types, generalized, 13. 


Use and disuse of organs, 73. 
Useless structures, how produced, 


76. 


Variation depends on sexual repro- 
duction, 238; caused by unfavor- 
able conditions, 264. 

Varieties, artificial production of, 
222, 235; artificial production of, 
illustrated, 224; natural and arti- 
ficial, compared, 228; origin of, 
unexplained, 270. 

“ Vestiges of Creation,” 34. 

Virtueand innocence compared, 372. 

Vital principle, 328. 

Voluntary social progress, 26. 


Weismann’s views, 93. 
Whales, rudimentary organs of, 
180, 


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USTICE: Being the First Part of Vol. II of “The 
Principles of Ethics.” 1vol. t2mo. Cloth, $1.25. 


*‘In a day when every reader is deeply absorbed in the debate over questions of 
ethics and the relations of man to man, such a work as this from the pen of one of the 
most profound of modern thinkers must make a wide and lasting appeal. Its appear- 
ance is a notable event in the annals of modern thought.” —PAzdladelphia Bulletin. 

‘<The history of nineteenth-century thought has offered few gratifications equal to 
that with which we view the approaching completion of Mr. Herbert Spencer’s system 
of synthetic philosophy.’’—Chicago Evening Fournal. 

““Mr. Spencer’s style is so lucid that to study political economy of him is rather a 
pleasure than a task,’’—Chicago Tribune. 


OCTAL STATICS. New and revised edition, in- 
cluding ‘‘The Man versus The State,” a series of essays on 
political tendencies heretofore published separately. 1r2mo. 
420 pages. Cloth, $2.00. 


Having been much annoyed by the persistent quotation from the old edi- 
tion of ‘‘ Social Statics,” in the face of repeated warnings, of views which 
he had abandoned, and by the misquotation of others which he still holds, 
Mr. Spencer some ten years ago stopped the sale of the book in England and 
prohibited its translation. But the rapid spread of communistic theories 
gave new life to these misrepresentations ; hence Mr. Spencer decided to 
delay no longer a statement of his mature opinions on the rights of individuals 
and the duty of the state. 


Contents: Happiness as an Immediate Aim.—Unguided Expediency.—The 
Moral-Sense Doctrine.—What is Morality ?—The Evanescence [? Diminution] of Evil. 
—Greatest Happiness must be sought indirectly.—Derivation of a First Principle.— 
Secondary Derivation of a First Principle —First Principle.—Application of this First 
Principle. —The Right of Property.—Socialism.—The Right of Property in Ideas.— 
The Rights of Women.—The Rights of Children.—Political Rights,—The Constitution 
of the State.—The Duty of the State.—The Limit of State-Duty.—The Regulation of 
Commerce.—Religious Establishments.—Poor-Laws.—National Education.—Govern- 
ment Colonization.—Sanitary Supervision.—Currency, Postal Arrangements, etc.— 
General Considerations.—The New Toryism.—The Coming Slavery.—The Sins of 
Legislators.—The Great Political Superstition. 


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NEW EDITION OF SPENCER’S ESSAYS. 
SSAYS: Scientific, Political, and Speculative. By 


HERBERT SPENCER. A new edition, uniform with Mr. Spencer’s 
other works, including Seven New Essays. Three volumes, 
12mo, 1,460 pages, with full Subject-Index of twenty-four pages, 


Cloth, $6.00, 


CONTENTS OF VOLUME I. 


The Development Hypothesis. 
Progress: its Law and Cause, 
Transcendental Physiology. 

The Nebular Hypothesis, 

Illogical Geology. 

Bain on the Emotions and the Will, 


The Social Organism. 

The Origin of Animal Worship. 
Morals and Moral Sentiments, 

The Comparative Psychology of Man, 
Mr. Martineau on Evolution. 

The Factors of Organic Evolution.* 


CONTENTS OF VOLUME II. 


The Genesis of Science. 

The Classification of the Sciences. 

Reasons for dissenting from the Phi- 
losophy of M, Comte, 

On Laws in General, and the Order 
of their Discovery. 

The Valuation of Evidence, 

What is Electricity ? 

Mill versus Hamilton—The Test of 
Truth. 


Replies to Criticisms. 

Prof. Green’s Explanations. 

The Philosophy of Style.t 

Use and Beauty. 

The Sources of Architectural Types 
Gracefulness. 

Personal Beauty. 

The Origin and Function of Music. 
The Physiology of Laughter. 


CONTENTS OF VOLUME III. 


Manners and Fashion. 

Railway Morals and Railway 
Policy. : 

The Morals of Trade. 

Prison-Ethics. 

The Ethics of Kant. 

Absolute Political Ethics. 

Over-Legislation. 

Representative Government— 
What is it good for ? 





State-Tampering with Money and 
Banks 

Parliamentary Reform: the Dangers 
and the Safeguards. 

‘¢ The Collective Wisdom.” 

Political Fetichism. 

Specialized Administration. 

From Freedom to Bondage. 

The Americans, t 

Index. 


* Also published separately. 1z2mo. Cloth, 75 cents. 
+ Also published separately, 12mo. Cloth, 50 cents, 
t Also published separately. 12mo, Paper, ro cents; cloth, so cents, 





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HE ICE AGE IN NORTH AMERICA, and its 
Bearings upon the Antiquity of Man. By G. FREDERICK 
Wricut, D.D., LL.D., F.G.S.A., Professor in Oberlin 
Theological Seminary; Assistant on the United States Geo- 
logical Survey. With an appendix on “The Probable Cause 
of Glaciation,” by WARREN Upuam, F.G.S.A., Assistant on 
the Geological Surveys of New Hampshire, Minnesota, and 
the United States. New and enlarged edition. With 150 Maps 
and Illustrations. 8vo, 625 pages, and Index. Cloth, $5.co. 


“Not a novel in all the list of this year’s publications has in it any pages of more 
thrilling interest than can be found in this book by Professor Wright. ‘There is noth- 
ing pedantic in the narrative, and the most serious themes and startling discoveries are 
treated with such charming naturalness and simplicity that boys and girls, as well as 
their seniors, will be attracted to the story, and find it difficult to lay it aside.” —New 
York ¥ournal of Commerce. 


“‘ One of the most absorbing and interesting of all the recent issues in the depart- 
ment of popular science.” —Chicago Herald. 


“Though his subject is a very deep one, his style is so very unaffected and per- 
spicuous that even the unscientific reader can peruse it with intelligence and profit. In 
reading such a book we are led almost to wonder that so much that is scientific can be 
put in language so comparatively simple.”—New York Observer. 

‘“¢ The author has seen with his own eyes the most important phenomena of the Ice 
age on this continent from Maine to Alaska. 1n the work itself, elementary description 
is combined with a broad, scientific, and philosophic method, without abandoning for 
a moment the purely scientific character. Professor Wright has contrived to give the 
whole a philosophical direction which lends interest and inspiration to it, and which in 
the chapters on Man and the Glacial Period rises to something like dramatic intensity.” 
—The Independent. 

“*. . . To the great advance that has been made in late years in the accuracy and 
cheapness of processes of photographic reproduction is due a further signal advantage 
that Dr. Wright’s work possesses over his predecessors’. He has thus been able to 
illustrate most of the natural phenomena to which he refers by views taken in the field, 
many of which have been generously loaned by the United States Geological Survey, 


in some cases from unpublished material; and he has admirably supplemented them by 
numerous maps and diagrams.”’—The Nation. 


~ 


oat AN DiTHE GLACIAL PERIOD Dampy ates 

FREDERICK WRIGHT, D.D., LL. D., author of “The Ice 
Age in North America,” “ Logic of Christian Evidences,” etc. 
No. 69, International Scientific Series. With numerous IIlus- 
trations. I2mo. Cloth, $1.75. 

Every one is interested in ancestry, yet the roots of family trees have not 
struck down to the Glacial period, and we are left to wonder regarding the 
manners and customs of our ancestors in the remote age of ice. Who and 
what these ancestors were, is told us in simple, entertaining, popular style 


by Professor Wright, and his fascinating narrative is re-enforced by a multi- 
tude of illustrations, 


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MODERN SCIENCE SERIES. 
Edited by Sir JoHN LUBBOCK, Bart., F.R. S. 


The works to be comprised in the ‘‘ Modern Science Series” are primarily not for 
the student, nor for the young, but for the educated layman who needs to know the 
present state and result of scientific investigation, and who has neither time nor inclina- 
tion to become a specialist on the subject which arouses his interest. Each book will 
be complete in itself, and, while thoroughly scientific in treatment, its subject will as 
far as possible be presented in language divested of needless technicalities. Ilustra- 
tions will be given wherever needed by the text. ‘Lhe following are the volumes thus 
far issued. Others are in preparation. 


7 ‘HE CAUSE OF AN ICE AGE. By Sir Ropert 
BAutt, LL. D., F.R.S., Royal Astronomer of Ireland, author of 
“Starland.” r2mo. Cloth, $1.00. 


** Sir Robert Ball’s book is, as a matter of course, admirably written. Though buta 
small one, it is amost important contribution to geology.” —London Saturday Review. 


“A fascinating subject, cleverly related and almost colloquially discussed.” —/P/zla- 
aelphia Public Ledger. 


j Pega HORSE: A Study in Natural History. By 
WILLIAM H. FLOWER, C. B., Director in the British Natural 
History Museum. With 27 Illustrations. 12mo. Cloth, $1.00. 


** The author admits that there are 3,800 separate treatises on the horse already pub- 
lished, but he thinks that he can add something to the amount of useful information 
now before the public, and that something not heretofore written will be found in this 
book. The volume gives a large amount of information, both scientific and practical, 
on the noble animal of which it treats.’ —New York Commercial Advertiser. 


7 “HE OAK: A Study in Botany. By H. MArsHALL 
WarpD, F.R.S. With 53 Illustrations. I2mo. Cloth, $1.00. 


“An excellent volume for young persons with a taste for scientific studies, because 
it will lead them from the contemplation of superficial appearances and those generalities 
which are so misleading to the immature mind, to a consideration of the methods of 
systematic investigation.” —Bostonx Beacon. 


‘From the acorn to the timber which has figured so gloriously in English ships 
and houses, the tree is fully described, and all its living and preserved beauties and 
virtues, in nature and in construction, are recounted and pictured.” —Lvooklyn Eagle. 


THNOLOGY IN FOLKLORE. By GEORGE 
LAWRENCE GomME, F.S.A., President of the Folklore Society, 
etc. 12mo. Cloth, $1.00. 


This book is an attempt to ascertain and set forth the principles upon 
which folklore may be classified, in order to arrive at some of the results 
which should follow its study, giving the subject the importance it deserves 
in connection with researches in ethnology. 


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VOLUTION IN SCIENCE, PHILOSOPHY, 
AND ART. A Series of Seventeen Lectures and Discussions 
before the Brooklyn Ethical Association. With 3 Portraits. 
466 pages. I2mo. Cloth, $2.00. Separate Lectures, in pam- 
phlet form, 10 cents each. 

These popular essays, by some of the ablest éxponents of the doctrine of 
evolution in this country, will be read with pleasure and profit by all lovers 
of good literature and suggestive thought. The principle of evolution, being 
universal, admits of a great diversity of applications and illustrations ; some 
of those appearing in the present volume are distinctively fresh and new. 

CONTENTS. 
. Alfred Russel Wallace . . . . . . By EDWARD D. COPE, Ph. D. 
. Lernst Haeckel. 5 ee 0 ia. 8. 4 oe BY THADDEUS BLOW ARE MARE 
~ Lhe Sctentific Method, . << . 4's + BYFRANGIS ho ApeOT a oe 
. Herbert Spencer's Synthetic Philosophy. By BENJ. F. UNDERWOOD, 
. Evolution of Chemistry . . . . « . By ROBERTG. ECCLES, M.D. 


. Evolution of Electric and Magnetic Physics. 
By ARTHUR E. KENNELLY. 


~ Lvolution Of Bolany? 3.6. ee? BY FRED JOWULIING cia 
. Zodlogy as related to Evolution . . . By Rev. JoHN C. KIMBALL, 
. Form and Color in Nature . . . . By WILLIAM POTTS, 

to, Optics as related to Evolution . . . ByL.A.W.ALLEMAN, M. D- 
BU POMMLIOI IOS APE! OS ite gt y's Lieb at, ay JOM ee 

12. Evolution of Architecture . . . . . ByRev. JOHN W. CHADWICK, 
13. Evolution of Sculpture . . . . . « By Prof. THomas DAVIDSON, 
14. Evolution of Painting . . . . . ». By FORREST P. RUNDELL, 


Am BW DN 


oOo on 


15. Evolution of Music . ... . . . By Z. SIDNEY SAMPSON. 
16, Life asa Fine Art... . . ». . By Lewis.G. JANES, M:D., 


17. Lhe Doctrine of Evolution : its Scope and Influence. 
By Prof. JOHN FISKE. 


“*A valuable series.” —Chicago Evening Yournal. 


caw LDS addresses include some of the most important presentations and epitomes pub- 
lished in America. They are all upon important subjects, are prepared with great care, 
and are delivered for the most part by highly eminent authorities ”—Pxdlic Opinion. 
** As a popular exposition of the latest phases of evolution this series is thorough and 
authoritative.” —Cixcinnatt Times-Star. 


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